Ok, a little update.
Downgrading to the 450 package as suggested here:
Does make my monitor behave as it should.
Although I think other problems appear. As for example temporary no internet connection. Probably it’s got something to do with a gdm3 crash. But I really don’t know what I’m typing about.
Thanks a lot for this forum Nvidia. But quality of support and availability of good drivers is not in line with product prices.
Of course this is only an opinion (based on use of Ubuntu 20.04 - 20.10 and Windows 10 (with audio problems)).