Good morning folks,
Trying to share a calendar this morning with a federated user, but no federated users are showing up when I search for them in the share dialog.
Can’t find any meaningful logs either in NC or in NGINX.
Any thoughts or suggestions?
Related to Trouble with federated calendar shares (Is still an issue.)
see also See calendar from another nextcloud instance with authentication
Now I found this: Share Calendar over Federated-Cloud-ID where it says, it was scheduled for Nextcloud 13.
If I follow the provided link to the github issue (Federated calendar and contacts sharing [$360.00] · Issue #1440 · nextcloud/server · GitHub) I find it still open and with a bounty of 360$.
What would be needed to make it finally happening?
Hi! 
It isn’t supported yet, as you’ve found. Federation is difficult and still very much a work in progress. You can read the long running github thread or search the forum for more discussions on federation, but the latest on it is support for Circles app in federating users as of nc25. It is a precursor step towards the possibility of eventually supporting calendar federation afaik.
A related overview Github Issue: Overview: Calendar Sharing · Issue #20096 · nextcloud/server · GitHub
(Beyond that, in https://github.com/nextcloud/server/pull/9345 it is mentioned at the end, that the problem should almost be solved… But no-one reacted on that. Let’s hope.)