Nice Tutorial, it works!
But one thing:
After updating everything, the Key Manager Service (stores the password) does not start reliable before the nextcloud client. As result, sometimes Nextcloud opens and asks for the password. Sometimes the Services starts fast enough and it works. Strange.
Maybe this could be solved with a nextcloud update, but there is no easy function for that. Im compiling the newest version right now, but isnt there an easier way to do this within the normal apt-get update process? Or, if not, an automatic Update Script or something like that?