If I have a new calendar with no entries and I export that calendar and then try to import that calendar into Nextcloud, it hangs showing the scheduling message. If I add a test event and then export and import that same file, it loads just fine. So it appears that nextcloud has a bug when it tries to import a generally empty calendar file.
Otherwise, everything else works pretty good. I switched from owncloud to nextcloud. Looking forward to more changes and improvements.
Keep up the good work!