Yup! I set up an !ownCloud server in 2013 (?) specifically to divorce myself from Google Calendar. I disliked the ownCloud calendar webUI; the !Nextcloud calendar webUI is only slightly better. But the backend implements the iCalendar spec RFC 5545 very well, so I'm using Thunderbird's Lightning caledendar plugin, the DAVdroid app from !Fdroid, and have used the .ics public access URI for other implementations. #GoogleFree