Since updating to Sonoma and using XCode 15.0.1 to adapt my app's code base to deal with new requirement for Full Access to calendars, I am simply unable to find ANY valid calendars of type EKEntityTypeEvent despite having about 8 different EKSources available (which I can see and access in the macOS Calendar app), and which do contain calendars I used to be able to read/write to before I updated to Catalina. But the call to EKSource's calendarsForEntityType function always returns nil.
I have successfully obtained Full Access permission (which in any case is obviously so because otherwise I would not get access to all the EKSource items). I've also rebooted several times. I have Calendar selected under Resource Access items for the app's capabilities.
Does anyone have any idea why, or a workaround? Looks like a potentially serious bug at this point.