I use CalDav for calendar, contacts and tasks sync and share with the rest of the family.
Server is Nextcloud with WebDav/WebCal/CardDav and DavX5, Etar calendar, native contacts and OpenTasks on android. On Linux WebDav to access and sync Nextcloud files.
How do you use them?
Edit: Added CardDav for contacts.
Floccus is nice to sync browser bookmarks via Webdav (it also has a Nextcloud addon)
In general there are a lot of note taking apps that allow syncing notes via Webdav. I recently came accross this one which works quite nicely: https://f-droid.org/en/packages/io.github.quillpad/
Nice. Gonna check it out.