Hm, yes, indeed, running it as root returns device information correctly.
I set the permissions of the computer to “secure” in YaST, and now running it as non-root results in an error:
cudaGetDeviceCount returned 100
→ no CUDA-capable device is detected
Result = FAIL
That now is true also for nvidia-smi, as a regular user it gives me:
Failed to initialize NVML: Insufficient Permissions
Even if I add myself into the video group, it’s still the same. Running as root works. So it seems to be a permissions problem indeed…