I’m stumped. I tried enabling iCloud reminders again so I could upgrade the list and now the group “Nextcloud” appears but no lists and no reminders in it. I tried deleting the Nextcloud profile and installing it again but it didn’t help (the group Nextcloud still appears though). Force refreshing from the Calendar app also does nothing. Thanks for testing though. I’ll update if I find anything new.
I can only provide the access logs from syncing calendars
ip.address.of.phone - - [18/Oct/2019:16:38:33 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/contact_birthdays/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:33 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/contact_birthdays/ HTTP/1.1" 207 7729
ip.address.of.phone - - [18/Oct/2019:16:38:33 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/work/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:33 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/work/ HTTP/1.1" 207 1636
ip.address.of.phone - - [18/Oct/2019:16:38:34 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/eth_timetable_20190921ics/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:34 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/eth_timetable_20190921ics/ HTTP/1.1" 207 42362
ip.address.of.phone - ME [18/Oct/2019:16:38:34 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/eth_timetable_20190921ics/ HTTP/1.1" 207 42812
ip.address.of.phone - ME [18/Oct/2019:16:38:35 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/eth_timetable_20190921ics/ HTTP/1.1" 207 42777
ip.address.of.phone - ME [18/Oct/2019:16:38:36 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/eth_timetable_20190921ics/ HTTP/1.1" 207 15041
ip.address.of.phone - - [18/Oct/2019:16:38:36 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/ethz/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:36 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/ethz/ HTTP/1.1" 207 3239
ip.address.of.phone - - [18/Oct/2019:16:38:37 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/personal/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:37 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/personal/ HTTP/1.1" 207 18270
ip.address.of.phone - ME [18/Oct/2019:16:38:38 +0200] "REPORT /nextcloud/remote.php/dav/calendars/ME/contact_birthdays/ HTTP/1.1" 207 18930
ip.address.of.phone - - [18/Oct/2019:16:38:38 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/inbox/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:38 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/inbox/ HTTP/1.1" 207 421
ip.address.of.phone - ME [18/Oct/2019:16:38:38 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/inbox/ HTTP/1.1" 207 421
ip.address.of.phone - - [18/Oct/2019:16:38:54 +0200] "REPORT /nextcloud/remote.php/dav/principals/users/ME/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:54 +0200] "REPORT /nextcloud/remote.php/dav/principals/users/ME/ HTTP/1.1" 207 560
ip.address.of.phone - - [18/Oct/2019:16:38:54 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/ HTTP/1.1" 401 557
ip.address.of.phone - ME [18/Oct/2019:16:38:54 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/ HTTP/1.1" 207 24908
ip.address.of.phone - ME [18/Oct/2019:16:38:54 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/inbox/ HTTP/1.1" 207 421
ip.address.of.phone - ME [18/Oct/2019:16:38:54 +0200] "PROPFIND /nextcloud/remote.php/dav/calendars/ME/inbox/ HTTP/1.1" 207 421