I have the same bug on my macOS Monterey-12.6 (M1) + Microsoft Remote Desktop 10.7.9 (2011).
Remote desktop hangs several times per day (the mouse cursor becomes a spinning wheel).
I use Microsoft Remote Desktop on macOS (M1) to remote login to a Linux machine (xubuntu-18.05.6).
When Microsoft Remote Desktop hangs, I see that the slack client also always hangs.
When I kill Microsoft Remote Desktop, slack recovers.
The issue is not with slack since Microsoft Remote Desktop also often hangs when I don't run the slack client.