plymouth boot screen hang

Sometimes, usually after a kernel update, the plymouth boot screen will spin endlessly. This is fixed by replacing `splash` with `plymouth.enable=0` temporarily in GRUB, then booting. It goes away until the next kernel update after you disable plymouth once.

Log from first successful boot: https://paste.cachyos.org/p/ce1655c.log

Also, not sure if it's related, but grub has a very slow input/render loop. When it comes on the screen, it renders row by row and takes like a whole second to render fully. Additionally, when trying to edit the boot config in the TUI, it also takes a second for a single keyboard input to reach the screen, even when you hold the key down (i.e. right arrow to move the cursor all the way to the end of the line to overwrite `splash`). typing too fast causes keypresses to just get completely missed.

Start by reviewing the linked boot log and reproducing the Plymouth hang after a kernel update, using the temporary GRUB change described in the issue. Investigate whether the Plymouth failure and slow GRUB rendering/input are related; done means identifying the cause and confirming a fix across the affected boot paths.

Written by the indexing model from the issue text.