I still can’t convince the nvidia-390xx-dkms to work, so I have to go with Linux 6.11.9-arch1-1 for now. In the booting process the machine does not even reach SDDM, although I’m still able to switch to a console using Strg+Alt+F key. Unluckily I had no time yet to dig deeper. Maybe it is because of my very old GPU. I used to run this machine with Nouveau until quite recently, but one or two major kernel versions earlier the PC started to crash in random intervals. Running the proprietary driver solved this issue, just to give me some more headache now.
I already locked kernel 6.11. This is working fine, but it would be nice to use the latest stuff.
The advantage of linux-lts would for sure be, that it receives security updates, which a locked (non-updated) kernel does not get.
It might be worth considering and retrying when the patch for kernel 6.13 is available. Maybe somebody comes up with an idea in the meantime.
I’m back to Nouveau now, which I do prefer anyway. With the latest kernel (6.13.0-rc3-1-mainline) it seems to run stable. At least for now. I assume I need to buy a new machine in the foreseeable future anyway. This will most likely include an Arc GPU (Battlemage), which will avoid proprietary problems in the future.