To reproduce the bug (Mac OS Big Sur 11.6.1, but also happened on Catalina): 1. Load Slack 2. Use Microsoft Remote Desktop by remoting into another machine. Make sure "Clipboard" is enabled. ...
I have the clipboard deselected now, which is not exactly convenient, but it seemed to fix the problem. Unfortunately, the crashes started again today. It always requires a force-quit of both apps, which is frustrating. However, I found that avoiding going directly from Remote Desktop to Slack, and instead clicking on another application between, can help to avoid crashes.