I want to build and gert linux-signed-imge-5.4.0-75.deb but I didn't know how canI to do

Why do you want to re-build a kernel version that is already existing?

See https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel for general instructions.

following https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel .I did , run `fakeroot dh binary` can not get linux-image-signed-5.4.0.75.deb

following https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel .I did , run `fakeroot dh binary` can not get linux-image-signed-5.4.0.75.deb

Please close as a duplicate of
https://answers.launchpad.net/ubuntu/+source/linux-5.7/+question/697535

Where do you see the command "fakeroot dh binary" in https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel ?

I suggest that you try "fakeroot debian/rules binary"

And furthermore you seem to misunderstand the package names.

Nowadays the package
linux-image-5.4.0-75-generic_5.4.0-75.84_amd64.deb
contains the signed kernel and
linux-image-unsigned-5.4.0-75-generic_5.4.0-75.84_amd64.deb
is the unsigned one.

 "fakeroot debian/rules binary" I tried. The package linux-image-unsigned-5.4.0-75-generic_5.4.0-75.84_arm64.deb has built,but the signed kernel deb has not built

What did you download?

following this

git clone https://kernel.ubuntu.com/git/ubuntu-stable/ubuntu-stable-focal.git

git clone https://kernel.ubuntu.com/git/ubuntu/ubuntu-focal-signed.git

cd ubuntu-focal-signed.git
 rsync -a ./* ../ubuntu-stable-focal.

following this

git clone https://kernel.ubuntu.com/git/ubuntu-stable/ubuntu-stable-focal.git

git clone https://kernel.ubuntu.com/git/ubuntu/ubuntu-focal-signed.git

cd ubuntu-focal-signed.git
 rsync -a ./* ../ubuntu-stable-focal.

But didn't get linux-image-signed-5.4.0-75-generic_5.4.0-75.84_arm64.deb

Can we please just have one question for thiss issue and maybuse this one. He's made about 8 questions for the same issue. So annoying

Thanks Manfred Hampl, that solved my question.