I don’t think the issue is fixed (yet), but I have found a workaround that at least seems to work in the Davx5 app (free from F-Droid store).
In the field of the base URL, use https://my.opendesktop.org/remote.php/dav/principals/users/<username>/ and everything will load! (CalDAV + tasks, CardDAV,).
(After adding the account, select which clendars, contact lists, etc. you want to show and then manually sync it by hitting the sync button). I hope this helps until things are fixed.