I wrote a few patches for uploading and downloading .ics files. I have them in the commit history at https://bgstack15.ddns.net/cgit/radicaleinfcloud/log/?h=stackrpms.
So far I've noticed that if an .ics file I wish to import (by dragging onto the "import" button of the new-event dialog, not documented properly iirc) does not contain a UUID, the upload silently fails and I have to check the backend server logs to see why it didn't like the event.
B. Stack