Big Sur 11.0: How to get BBM installed and working?

I have read and tried the suggestions on these fora as well as the the Apple instructions on opening unidentified developer apps. I unfailingly get “BBManager will damage your computer. You should move t to the trash.” I simply cannot find a way around this and have spent too ,any hours trying. Sure could use advice that will work.

The instructions state that if all else fails, contact Support.