suspend works

resume display is blank

You can see something like that:

cp: cannot stat '/lib/firmware/updates/amdgpu': No such file or directory
I: The initramfs will attempt to resume from /dev/dm-2
I: (/dev/mapper/vgubuntu-swap_1)
I: Set the RESUME variable to override this.

Possible solution:

The swap UUID needs to be added to the /etc/initramfs-tools/conf.d/resume file.

The following command can show what your swap UUID is:

blkid | awk -F\" '/swap/ {print $2}'

You can run the following to set that in the RESUME file (it will be created if it doesn't exist in that folder):

printf "RESUME=UUID=$(blkid | awk -F\" '/swap/ {print $2}')\n" | sudo tee /etc/initramfs-tools/conf.d/resume

Then run the following to update the kernels on the system:

sudo update-initramfs -u -k all

End of line.

source: https://askubuntu.com/questions/1116778/how-to-set-the-resume-variable-to-override-these-issues