Grub unable to boot Ubuntu when using theme with PNG images

[Allan Crooks]

I normally use Linux Mint, but I tested the behaviour with Ubuntu and saw the same results.

The problem seems to occur when:
 - I use Grub installed by Ubuntu 20.04.
 - I install a Grub theme which has PNG images in it.
 - I try to boot into an Ubuntu 20.04 OS.

When I select the OS from the menu, the screen just goes black and remains that way. If I run it using the other options (where I can see the output), the last thing it prints is "Loading initial ramdisk..." and then just hangs there.

To avoid this problem, I can:
 - Boot into an Ubuntu 18.04 OS - the problem doesn't seem to occur there.
 - Manually remove references to images in the theme file.

I'm trying this on a Dell XPS 9380. It didn't matter if I was using a newer kernel (5.4.0-40) or the default one upon install (5.4.0-26). It wasn't specific to the installation, since I had multiple installs trying to debug the issue (both of Linux Mint and Ubuntu).

I tested with the grub2-theme-mint-2k package, but then also tried downloading other themes from other sites and saw the same issue. Removing the references to the png images in the file allowed it to work - it didn't seem to matter that the "insmod png" line was still present.

And it's also really strange that it only seemed to affect Ubuntu 20.04, but not 18.04 (using kernel 5.3.0-59). I haven't seen anyone else complain about such a thing, so I don't know if it's something highly specific to my setup that's causing it.

[Allan Crooks (allan-crooks)]

The full grub.cfg file which doesn't work for me.