I’m not really sure which correction actually solved the problem. The discussion went on for quite some time: KDE Linux: Editing fstab not possible
- I first edited the fstab file directly in Dolphin. Following a tip, I tried using Nano in the terminal, which worked better.
- Then I had created the “mount” directories incorrectly (the underlying “media” directory was missing).
After that, I actually gave up and didn’t look at it for a long time. After a few updates, I tried again and it worked right away (maybe cifs-utils was updated).