I strongly advise against testing betas on your main / production instance. Matter of fact, I would usually even recommend to wait at least until the first point release, before upgrading to a new major release.
These are all third party apps, so there isn’t much the Nextcloud developers can do. After all they cannot force independent app developers to upgrade their apps on time.
Visiting the web frontend greeted me with an app update message. Clicking on the only button resulted in a longish list of repair steps the system executed on its own.
Everything seems to work!
I’m impressed! Thanks a lot!