Since Linux 6.15, screen brightness on Plymouth decrypt is very low

OS: Arch Linux
Updated: To 13th of June, 2025
Kernel: 6.15.2
BIOS: 3.09
Model: Framework 13, Ryzen 5 7640

Hi there, I use Arch Linux with Plymouth and the sd-encrypt hook to write the disk passphrase on boot.

I’m not sure what has changes on 6.15, but since then, the screen brightness is very low during all that process, including the passphrase input step. After that while loading the desktop, brightness goes up, probably to what it was set on the Gnome desktop.

I’ve got a second Lenovo laptop with exact same installed software, and it’s not happening there. Not sure if something has changed regarding the screen brightness on 6.15.