When trying to select NVidia driver version 530 from the "Software & Updates" settings, I'm getting this window:
Most likely, it wants to tell me that something went wrong, because it automatically switches back to the previously selected driver version.
Is this a known issue with a work-around?
It turned out that a reboot seems to have solved the issue. After the reboot, Ubuntu had switched to the Xorg driver, which may indicate that temporarily switching to the Xorg driver may be necessary.
It then required yet another reboot for the 530 driver version to actually become active and properly appear in nvidia-smi.
This answer may be also helpful in the context of debugging the problem.