https://bugzilla.kernel.org/show_bug.cgi?id=200607
--- Comment #2 from Parker Reed (parker.l.reed@gmail.com) --- I'm streaming via Steam in-home streaming and occasionally a fullscreen application will mess things up. When I reboot, SDDM/Plasma hang because of that driver crash. Leaving the up to date firmware files in there, it comes back after a couple reboots (randomly), and continues to work for a while. For now I have just downgraded back to my distro shipped linux-firmware.
I'm not sure if the fullscreen issue is related but I know it definitely causes SDDM/Plasma init to freak out. So I'd say that's when it hangs the most for me.