Unable to Set iCloud Calendar as Default After BigSur Upgrade

[coincollector82]

After upgrading to BigSur I've found I'm unable to set my iCloud calendar as default in the Calendar app. When I receive an ICS file the Calendar app creates a new calendar. Once the event is created on the new calendar I am able to move it to iCloud. Before the upgrade my iCloud calendar was default and working as expected. I've tried removing the iCloud account from Calendar and adding it back without success. Has anyone else seen this, and have you found a solution?

Note: When I remove iCloud from Calendar the local "On this Mac" calendars appear in the default selection list. So it is only iCloud calendars missing from the selection.

 

[coincollector82]

I found a workaround for anyone interested. When a received ICS file creates a new calendar called "Mail Attachments" both the new and original calendars show up as options to set as default. However, once the new calendar is deleted both of them disappear from the drop down. So, if you don't mind having an unused second calendar then this should work until a fix is provided.