Today I switched to an Xorg-based GNOME session, and found out that invoking `xset dpms force off` also results in the system freezing. Interestingly, the system was responsive via ssh for another couple seconds or so.
So I think this regression must be related to the kernel version change more than anything else. Reassigning the bug.
Again, I'd be more than happy to do whatever is needed to investigate this deeper. The only idea comes to mind is to try and bisect the kernel history between 5.10.179-2 and 6.1.38-4, but I'm not sure how feasible it is these days (it's been almost two decades since I last built my own kernel package and don't know what config to use between these two versions).