First, I can't see how any of the 3 packages updated would be in any way responsible.
I assume you've already booted at least once more.
I tried 3-4 times.
Have you also re-seated video cables? I've had unexplained video issues cleared up by doing that.
The screen is not the issue because I get the ssdm login screen perfectly well. Also it's a laptop with an external screen. I have tested with and without the external screen plug-in, same behaviour.
You haven't accidentally tried to open a Plasma KDE session under wayland, have you?
I do not know wayland. I do not know how to open plasma under wayland.
Is your Logon session set to "Restore Previous Session", "Restore Manually Saved Session", or "Start Empty Session"?
I do not remember. I turned the computer off automatically after backup. When I leave, I open a terminal, su to root, run dnf update, run my backup command followed by "; shutdown" so that the computer turns off automatically.
I tried to launch systemsettings5 from another computer but I get a buggy window: $ ssh -X alpha systemsettings5 libGL error: No matching fbConfigs or visuals found libGL error: failed to load driver: swrast
Since you can get to a text terminal. Have you tried creating another user and then logging in as that user?
just done it, same problem with the new user
Frédéric