Since around the middle of October 2020, my Arch Linux machines don't wake up the monitor anymore when I press any key in the Gnome login screen. However the machine itself is woken up, as I see my keypresses as password entries or am even locked if I press enter due to too many login attempts once I wake the monitor up by switching to another console via CTRL+ALT+Fx and back.

What has changed and how can I restore the original functionality?