I was able to fix the problem. It was as faulty version of GDM that was released yesterday. Version 3.26.2 tries to start a Wayland session by default which is impossible with the NVDIA drivers.
Here’s the corresponding thread
So what I did was booting directly into the system without a graphical environment by adding “systemd.unit=multi-user.target” to the kernel command. For some reason I was able to run pacman -Syyu this time, however this didn’t solve it.
I had to downgrade GDM via sudo pacman -U /var/cache/pacman/gdm-3.26.1-1-x86_64.pkg.tar.xz
After reboot, I was back on my desktop :)
I have one question though. How do I navigate/browse (blättern) in an “ls” list when it is very long so that the content doesn’t fit on the monitor. I was trying to find the exact name of the GDM package but the list was so long that the opackages with “g” weren’t visible.