Ubuntu 18.04 Nvidia nForce 630a Driver Issue

Are you planning to game in Linux?

Not really. I intend to use the machine for dev work mostly, but there is flickering sometimes and the animations are very slow with a lot of lagging. Garbled display in some portions of the screen sometimes etc.. Tried it on Ubuntu 19.10 as well and it's worse there.

If you run:

sudo apt-get install nvidia-current

does it install OK?

Doesn't work either. Here is the output:
-------------------------------------------------------------
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package nvidia-current is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'nvidia-current' has no installation candidate

Do you have the latest BIOS in the motherboard

Well, that's another battle. BIOS firmware is not updated. Actually, I think I never did update it and the system is pretty old. Every time I fire up the utility from BIOS (ASUS flash tool), the display goes black with a "monitor out of range" message which is probably a resolution issue with the GPU or something. I am not sure but I am trying to find a fix for that too and see if I can flash it with the latest update. I'm using a VGA monitor which is USB powered.

Try installing nvidia-driver-390. That should work, I think the latest package I ran on an n630 was 340, so try that if 390 does not work.

If you have ubuntu 18.04 LTS, stick to original kernel and do not upgrade to HWE kernel (the point release kernels)

Nvidia driver 304.137 is the last version that has support for this gpu, newer nvidia drivers dont support this old gpu as it's support has been deprecated

And driver 304.137 has only support for the original kernel version that shipped with ubuntu 18.04 not for the later ones such as that of 18.04.1 to 18.04.5 and for later ubuntu release such as 18.10, 19.04, 19.10, 20.04, 20.10, 21.04 and 21.10

There is no support after original 18.04 in short

I too am plagued by the same issue as I also have this motherboard

There is a way to install nvidia driver 304.137 (last for this gpu) in ubuntu 20.04, (non hwe one) that means only kernel upto kernel 5.4 via some patches but then you have to hold some older package versions that can cause DE to misbehave
And this patched nvidia driver does not install in kernel 5.8 that is in ubuntu 20.04 point releases

And since it is an old hardware you dont need newer kernels
I suggest you stick with Lubuntu 18.04 for your system
And use snap for updated softwares packages

I use nouveau (FOSS nvidia driver) included in every distro
But nouveau causes system crash when making the video go fullscreen or jumping while playing the video

If you can invest in an NVIDIA GEFORCE GT 710
That would be for the best
As nouveau works flawlessly on this particular card
Don't go for newer cards

I did the same

GT 710 works perfectly with nouveau driver
So I can always have the latest Lubuntu (21.10 right now)
Without any worries

But I am still looking into the nouveau crash on geforce 7025 issue, if there is any new findings, i will let you know