This sounds like a terribly mismanaged Workplace instance to me. Why should anyone be joined to 100 groups? That's a red flag right there. And if you can't move

This sounds like a terribly mismanaged Workplace instance to me. Why should anyone be joined to 100 groups? That's a red flag right there. And if you can't move personal stuff off of Workplace, create separate groups for that that can be muted or left etc. This noisy personal stuff can easily exist in public groups that can be looked into by anyone if something comes up.