Yes, have it running and it works well. Nextcloud setup is sth that I will still have to set up but the only problem I see there is certificates.
To debug Nebula, simply try executing it by hand, e.g. nebula --config /path/config.yml
and see what the error message is. Or check your journalctl of course. Share the message here and we can have a look!
I don’t see anything like that in this thread. If you want people’s help, help them help you and provide sufficient information about your problem.