FileCloud Drive version 21.1 and higher supports Catalina and Big Sur.Please note that for Drive running on Apple Silicon M1, Big Sur 11.3 or higher is required and security settings have to be adjusted.See FileCloud Drive: Configuration for Big Sur Running on Apple Silicon
If you are using Mac OS Big Sur, and you have trouble opening documents after installing or updating FileCloud Drive, do the following:
On a command line run:
sudo kextcache --clear-staging
When you open Drive, if the following message pops up, follow its instructions, restart your system if necessary, and then re-open Drive.