I was running Nextcloud 20.0.6 before yesterday, but my installation automatically updated to 20.0.7. Since then I don’t have apps such as Calendar, Contacts, Onlyoffice, Bookmarks, Notes, etc…
Afaik automatic updates doesn’t exist in Nextcloud yet, so someone need to have triggered the update. Check-out if the apps are still installed on your server or have been deleted at all. You can do this on the console using the occ command. If they’re still installed, you might need to reactivated it.
I think you’re wrong about updates. As long as I’ve been on on version 20.0.x or so, I get automatic updates on Sundays for minor versions, like 20.0.6 to 20.0.7.
Check-out the Nextcloud adminstrator guide, which describes the available update mechanisms. From what I can see there is no automatic update available by default. An administrator has to force any kind of update by setting-up a cron job etc.