So I tried to Upgrade from 9.1.2 to the 11 RC1 which is out shortly.
Nearly a perfect upgrade (by Terminal) but lost 2 apps because of incompatibility
passwords v19 or 20 beta6 makes no diff (not working)
ownNotes
Never the less -> the v11 of nextcloud with internal Version 10.0.6 did the trick for the upgrade 