It is indeed the kernel - I use Gnome Shell 48.x and don’t experience the issue anymore.
Something in the kernel was missing and caused the issue. Precompiled debian kernels worked for me, but building my own resulted in the issue.
@manuel I have this same issue with KDE Plasma, - but with resume on a full rig. Sliding the brightness control on the Display settings “resets” it for the session, so I’m not sure it’s specific to Gnome.
KDE Plasma Version: 6.5.3
KDE Frameworks Version: 6.20.0
Qt Version: 6.10.0
Kernel Version: 6.17.8-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 7800X3D 8-Core Processor
Memory: 64 GiB of RAM (62.4 GiB usable)
Graphics Processor: AMD Radeon RX 6700 XT
There may be many potential reasons, as seen on this thread.
Did you try the LTS kernel?
Or x11?
Not an issue on the LTS fallback.
Found this while researching the same with Gnome 49 and kernel 6.17.1, though I am on Bluefin Linux.
Basically I am on a hybrid i915/nvidia laptop and after suspend/resume I lose control of brightness (OSD shows when pressing keys, but backlight stays at same level).
Seems to be this issue in Gnome if anyone wants to follow: https://gitlab.gnome.org/GNOME/mutter/-/issues/4432
Suspicion is that when resuming the nvidia H/W is restored early and Gnome switches to using the incorrect sysfs interface (nvidia instead of i915).
EDIT: I found a workaround, check my comment in the issue if you want to try it.