I think I can build a workaround for the problems on Big Sur. I am confident the cloud functionality will be usable on that OS version with the next update 3.7.1.
But I am not quite sure about getting Catalina to work. I can see exactly where the crash happens but I have currently no idea why it does not work. I will wait for more crash logs from other users but as far as I can tell from the metrics I see on the App Store have been no active users on 10.15 in the last 3 months. At least none that allowed sharing some data with developers. So not sure I will get any additional crash reports that will shed a light on this as I will also not get any crash logs from users not sharing data with developers.