Synchronizing: How do you sync / synchronize Calendar and Contacts with your desktop?

[Anna]

I have found the problem: In order to make Gnome Contacts / Calendar share their entries with Nextcloud, one has to go to Settings/Change Address Book and select the Nextcloud-Calendar in Gnome Contacts -- and do the same when adding a new entry in Calendar.

So I guess I can mark the issue as solved now. In my brief experience, the  simplest way to synchronise contacts and dates between the Pinephone and a desktop computer is to

• install Ubuntu Server in Virtualbox and set up Nextcloud (which is easy and can be quickly done, there are loads of video tutorials)
  
• go to Settings/Online Accounts/Nextcloud on the Pinephone, add the server name etc and choose calendar/contacts and do the same on the computer.
  
• make sure one selects the Nextcloud address book and calendar in Gnome Contacts / Calendar (see above).
  

Now all entries should be synchonised and remain available when offline.