Can't print after upgrading to Ubuntu 20.04

Printer: HP LaserJet Professional M1212nf MFP over local network connection (wired)

Printer worked fine under Ubuntu 18.04. Upgraded to 20.04. Print jobs started failing.

I removed the apt hplip package, which was 3.20.3, and downloaded and installed 3.20.6 manually.

During installation, I got several of the following warnings:

    \Gtk-Message: 13:42:45.684: Failed to load module "canberra-gtk-module"

During plugin download phase, it could not connect to the keyserver. I downloaded without verification anyway and plugin installed ok. (I subsequently got it to download the verification key and install the verified plugin.)

During device setup, I got the following error:

Searching... (bus=net, timeout=5, ttl=4, search=(None) desc=0, method=slp)
error: Loading /usr/share/hplip/fax/plugins/fax_marvell.so failed. Try after installing plugin libraries

Run "hp-plugin" to installa plugin libraries if you are not automatically prompted

Traceback (most recent call last):
  File "/usr/share/hplip/ui5/setupdialog.py", line 1305, in NextButton_clicked
    self.showAddPrinterPage()
  File "/usr/share/hplip/ui5/setupdialog.py", line 729, in showAddPrinterPage
    self.readwriteFaxInformation()
  File "/usr/share/hplip/ui5/setupdialog.py", line 1100, in readwriteFaxInformation
    d = fax.getFaxDevice(self.fax_uri, disable_dbus=True)
  File "/usr/share/hplip/fax/fax.py", line 534, in getFaxDevice
    return MarvellFaxDevice(device_uri, printer_name, callback, fax_type, disable_dbus)
  File "/usr/share/hplip/fax/marvellfax.py", line 109, in __init__
    self.service.SendEvent(device_uri, printer_name, EVENT_FAX_FAILED_MISSING_PLUGIN, os.getenv('USER'), job_id, "Plugin is not installed")
AttributeError: 'NoneType' object has no attribute 'SendEvent'

hp-setup appeared to stall at that point and had to be closed before the print/fax queues dialog came up. A print queue was created anyway, but it appeared to have no properties and wasn't functional. No devices showed up in HP Device Manager. Obviously I can't print now.

Here is the output of hp-check -t:

hp-check[91575]: info: :
hp-check[91575]: info: :HP Linux Imaging and Printing System (ver. 3.20.6)
hp-check[91575]: info: :Dependency/Version Check Utility ver. 15.1
hp-check[91575]: info: :
hp-check[91575]: info: :Copyright (c) 2001-18 HP Development Company, LP
hp-check[91575]: info: :This software comes with ABSOLUTELY NO WARRANTY.
hp-check[91575]: info: :This is free software, and you are welcome to distribute it
hp-check[91575]: info: :under certain conditions. See COPYING file for more details.
hp-check[91575]: info: :
hp-check[91575]: info: :Note: hp-check can be run in three modes:
hp-check[91575]: info: :1. Compile-time check mode (-c or --compile): Use this mode before compiling the HPLIP supplied tarball (.tar.gz or .run) to determine if the proper dependencies are
hp-check[91575]: info: :installed to successfully compile HPLIP.
hp-check[91575]: info: :2. Run-time check mode (-r or --run): Use this mode to determine if a distro supplied package (.deb, .rpm, etc) or an already built HPLIP supplied tarball has the proper
hp-check[91575]: info: :dependencies installed to successfully run.
hp-check[91575]: info: :3. Both compile- and run-time check mode (-b or --both) (Default): This mode will check both of the above cases (both compile- and run-time dependencies).
hp-check[91575]: info: :
hp-check[91575]: info: :Check types:
hp-check[91575]: info: :a. EXTERNALDEP - External Dependencies
hp-check[91575]: info: :b. GENERALDEP - General Dependencies (required both at compile and run time)
hp-check[91575]: info: :c. COMPILEDEP - Compile time Dependencies
hp-check[91575]: info: :d. [All are run-time checks]
hp-check[91575]: info: :PYEXT SCANCONF QUEUES PERMISSION
hp-check[91575]: info: :
hp-check[91575]: info: :Status Types:
hp-check[91575]: info: : OK
hp-check[91575]: info: : MISSING - Missing Dependency or Permission or Plug-in
hp-check[91575]: info: : INCOMPAT - Incompatible dependency-version or Plugin-version
hp-check[91575]: info: :
hp-check[91575]: info: :
hp-check[91575]: info: :---------------
hp-check[91575]: info: :| SYSTEM INFO |
hp-check[91575]: info: :---------------
hp-check[91575]: info: :
hp-check[91575]: info: : Kernel: 5.4.0-42-generic #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020 GNU/Linux
 Host: thud
 Proc: 5.4.0-42-generic #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020 GNU/Linux
 Distribution: 12 20.04
hp-check[91575]: info: : Bitness: 64 bit

hp-check[91575]: info: :
hp-check[91575]: info: :-----------------------
hp-check[91575]: info: :| HPLIP CONFIGURATION |
hp-check[91575]: info: :-----------------------
hp-check[91575]: info: :
hp-check[91575]: info: :HPLIP-Version: HPLIP 3.20.6
hp-check[91575]: info: :HPLIP-Home: /usr/share/hplip
hp-check[91575]: info: :HPLIP-Installation: Auto installation is supported for ubuntu distro 20.04 version
hp-check[91575]: info: :
hp-check[91575]: info: :Current contents of '/etc/hp/hplip.conf' file:
hp-check[91575]: info: :# hplip.conf. Generated from hplip.conf.in by configure.

[hplip]
version=3.20.6

[dirs]
home=/usr/share/hplip
run=/var/run
ppd=/usr/share/ppd/HP
ppdbase=/usr/share/ppd
doc=/usr/share/doc/hplip-3.20.6
html=/usr/share/doc/hplip-3.20.6
icon=/usr/share/applications
cupsbackend=/usr/lib/cups/backend
cupsfilter=/usr/lib/cups/filter
drv=/usr/share/cups/drv/hp
bin=/usr/bin
apparmor=/etc/apparmor.d
# Following values are determined at configure time and cannot be changed.
[configure]
network-build=yes
libusb01-build=no
pp-build=no
gui-build=yes
scanner-build=yes
fax-build=yes
dbus-build=yes
cups11-build=no
doc-build=yes
shadow-build=no
hpijs-install=no
foomatic-drv-install=no
foomatic-ppd-install=no
foomatic-rip-hplip-install=no
hpcups-install=yes
cups-drv-install=yes
cups-ppd-install=no
internal-tag=3.20.6
restricted-build=no
ui-toolkit=qt5
qt3=no
qt4=no
qt5=yes
policy-kit=no
lite-build=no
udev_sysfs_rules=no
hpcups-only-build=no
hpijs-only-build=no
apparmor_build=yes
class-driver=no

hp-check[91575]: info: :
hp-check[91575]: info: :Current contents of '/var/lib/hp/hplip.state' file:
hp-check[91575]: info: :[plugin]
installed = 1
eula = 1
version = 3.20.6

hp-check[91575]: info: :
hp-check[91575]: info: :Current contents of '~/.hplip/hplip.conf' file:
hp-check[91575]: info: :[installation]
date_time = 08/18/20 13:42:44
version = 3.20.6

[upgrade]
notify_upgrade = true
last_upgraded_time = 1597781789
pending_upgrade_time = 0

[last_used]
device_uri = hp:/net/HP_LaserJet_Professional_M1212nf_MFP?ip=192.168.0.19
printer_name = HP_LaserJet_Professional_M1212nf_MFP

hp-check[91575]: info: : <Package-name> <Package-Desc> <Required/Optional> <Min-Version> <Installed-Version> <Status> <Comment>
hp-check[91575]: info: :
hp-check[91575]: info: :-------------------------
hp-check[91575]: info: :| External Dependencies |
hp-check[91575]: info: :-------------------------
hp-check[91575]: info: :
hp-check[91575]: info: : cups CUPS - Common Unix Printing System REQUIRED 1.1 2.3.1 OK 'CUPS Scheduler is running'
hp-check[91575]: info: : gs GhostScript - PostScript and PDF language interpreter and previewer REQUIRED 7.05 9.50 OK -
hp-check[91575]: info: : xsane xsane - Graphical scanner frontend for SANE OPTIONAL 0.9 0.999 OK -
hp-check[91575]: info: : scanimage scanimage - Shell scanning program OPTIONAL 1.0 1.0.29 OK -
hp-check[91575]: info: : dbus DBus - Message bus system REQUIRED - 1.12.16 OK -
hp-check[91575]: info: : policykit PolicyKit - Administrative policy framework OPTIONAL - 0.105 OK -
hp-check[91575]: info: : network network -wget OPTIONAL - 1.20.3 OK -
hp-check[91575]: info: : avahi-utils avahi-utils OPTIONAL - 0.7 OK -
hp-check[91575]: info: :
hp-check[91575]: info: :------------------------
hp-check[91575]: info: :| General Dependencies |
hp-check[91575]: info: :------------------------
hp-check[91575]: info: :
hp-check[91575]: info: : libjpeg libjpeg - JPEG library REQUIRED - - OK -
hp-check[91575]: info: : cups-devel CUPS devel- Common Unix Printing System development files REQUIRED - 2.3.1 OK -
hp-check[91575]: info: : cups-image CUPS image - CUPS image development files REQUIRED - 2.3.1 OK -
hp-check[91575]: info: : libpthread libpthread - POSIX threads library REQUIRED - b'2.31' OK -
hp-check[91575]: info: : libusb libusb - USB library REQUIRED - 1.0 OK -
hp-check[91575]: info: : sane SANE - Scanning library REQUIRED - - OK -
hp-check[91575]: info: : sane-devel SANE - Scanning library development files REQUIRED - - OK -
hp-check[91575]: info: : libnetsnmp-devel libnetsnmp-devel - SNMP networking library development files REQUIRED 5.0.9 5.8 OK -
hp-check[91575]: info: : libcrypto libcrypto - OpenSSL cryptographic library REQUIRED - 1.1.1 OK -
hp-check[91575]: info: : python3X Python 2.2 or greater - Python programming language REQUIRED 2.2 3.8.2 OK -
hp-check[91575]: info: : python3-notify2 Python libnotify - Python bindings for the libnotify Desktop notifications OPTIONAL - - OK -
hp-check[91575]: info: : python3-pyqt5-dbus PyQt 5 DBus - DBus Support for PyQt5 OPTIONAL 5.0 5.14.1 OK -
hp-check[91575]: info: : python3-pyqt5 PyQt 5- Qt interface for Python (for Qt version 4.x) REQUIRED 5.0 5.14.1 OK -
hp-check[91575]: info: : python3-dbus Python DBus - Python bindings for DBus REQUIRED 0.80.0 1.2.16 OK -
hp-check[91575]: info: : python3-xml Python XML libraries REQUIRED - 2.2.9 OK -
hp-check[91575]: info: : python3-devel Python devel - Python development files REQUIRED 2.2 3.8.2 OK -
hp-check[91575]: info: : python3-pil PIL - Python Imaging Library (required for commandline scanning with hp-scan) OPTIONAL - 7.0.0 OK -
hp-check[91575]: info: : python3-reportlab Reportlab - PDF library for Python OPTIONAL 2.0 3.5.34 OK -
hp-check[91575]: info: :
hp-check[91575]: info: :--------------
hp-check[91575]: info: :| COMPILEDEP |
hp-check[91575]: info: :--------------
hp-check[91575]: info: :
hp-check[91575]: info: : libtool libtool - Library building support services REQUIRED - 2.4.6 OK -
hp-check[91575]: info: : gcc gcc - GNU Project C and C++ Compiler REQUIRED - 9.3.0 OK -
hp-check[91575]: info: : make make - GNU make utility to maintain groups of programs REQUIRED 3.0 4.2.1 OK -
hp-check[91575]: info: :
hp-check[91575]: info: :---------------------
hp-check[91575]: info: :| Python Extentions |
hp-check[91575]: info: :---------------------
hp-check[91575]: info: :
hp-check[91575]: info: : cupsext CUPS-Extension REQUIRED - 3.20.6 OK -
hp-check[91575]: info: : hpmudext IO-Extension REQUIRED - 3.20.6 OK -
hp-check[91575]: info: :
hp-check[91575]: info: :----------------------
hp-check[91575]: info: :| Scan Configuration |
hp-check[91575]: info: :----------------------
hp-check[91575]: info: :
hp-check[91575]: info: : hpaio HPLIP-SANE-Backend REQUIRED - 3.20.6 OK 'hpaio found in /etc/sane.d/dll.conf'
hp-check[91575]: info: : scanext Scan-SANE-Extension REQUIRED - 3.20.6 OK -
hp-check[91575]: info: :
hp-check[91575]: info: :------------------------------
hp-check[91575]: info: :| DISCOVERED SCANNER DEVICES |
hp-check[91575]: info: :------------------------------
hp-check[91575]: info: :
hp-check[91575]: info: :No Scanner found.
hp-check[91575]: info: :
hp-check[91575]: info: :--------------------------
hp-check[91575]: info: :| DISCOVERED USB DEVICES |
hp-check[91575]: info: :--------------------------
hp-check[91575]: info: :
hp-check[91575]: info: :No devices found.
hp-check[91575]: info: :
hp-check[91575]: info: :---------------------------------
hp-check[91575]: info: :| INSTALLED CUPS PRINTER QUEUES |
hp-check[91575]: info: :---------------------------------
hp-check[91575]: info: :
hp-check[91575]: info: :
hp-check[91575]: info: :<email address hidden>
hp-check[91575]: info: :----------------------------------------------------
hp-check[91575]: info: :Type: Unknown
hp-check[91575]: info: :Device URI: implicitclass://HP_LaserJet_Professional_M1212nf_MFP%40NPI91F125.local/
hp-check[91575]: info: :PPD: /<email address hidden>
warning: Failed to read /<email address hidden> ppd file
hp-check[91575]: info: :PPD Description:
hp-check[91575]: info: :Printer status: printer <email address hidden> is idle. enabled since Tue 18 Aug 2020 12:56:28 PM
warning: Printer is not HPLIP installed. Printers must use the hp: or hpfax: CUPS backend for HP-Devices.
hp-check[91575]: info: :
hp-check[91575]: info: :
hp-check[91575]: info: :--------------
hp-check[91575]: info: :| PERMISSION |
hp-check[91575]: info: :--------------
hp-check[91575]: info: :
hp-check[91575]: info: :
hp-check[91575]: info: :-----------
hp-check[91575]: info: :| SUMMARY |
hp-check[91575]: info: :-----------
hp-check[91575]: info: :
hp-check[91575]: info: :Missing Required Dependencies
hp-check[91575]: info: :-----------------------------
hp-check[91575]: info: :None
hp-check[91575]: info: :
hp-check[91575]: info: :Missing Optional Dependencies
hp-check[91575]: info: :-----------------------------
hp-check[91575]: info: :None

hp-check[91575]: info: :
hp-check[91575]: info: :Total Errors: 0
hp-check[91575]: info: :Total Warnings: 1
hp-check[91575]: info: :
hp-check[91575]: info: :
hp-check[91575]: info: :Done.

Thanks for any help you can provide!