Obscure bug or interaction between system components (hardware and software)
I opened the original bug at https://bugzilla.redhat.com/show_bug.cgi?id=2171289 , the whole story is there.
The hardware specs summary where the bug occurred was:
- quad core AMD 3xxx
- 16GB DDR3 RAM
- AMD RX6600
- spinning rust HDD - because of this, booting up took minutes
- LG 24MK400H - probably part of the problem, too, causing issues with the AMDGPU driver in the kernel(?)
The machine was running Fedora 37 at the time.
During booting up, probably due to the default power save settings in Fedora, the video output was turned off according to the monitor's OSD message, and shortly after the monitor switched to power save mode, blanking itself.
After booting finished (with auto-login enabled in GDM) the gnome-shell interface suddenly came on the monitor and worked with the original versions of gnome-shell builds shipped by Fedora 37.
At some point, when Fedora 37 shipped gnome-shell 43.3-1, the gnome-shell interface started in a state that it did not respond to mouse clicks.
Earlier versions were also tested, most of them without issues. Upgrading to 43.3-1 always brought back the problem.
The problem was probably caused by the wildly asymmetric nature of the machine, with HDD causing very long boot times and probably some delays timing out somewhere. The HDD itself is in a good state, but still slow compared to other parts of the system.
Since then that particular machine was replaced by a newer and faster one with NVME SSD, so booting is lightning fast. The monitor was not replaced. This particular problem does not occur anymore on the new machine.
FWIW, testing is probably not worth pursuing as HDDs as system drives are not that common anymore.