Comment by Hobadee

This isn't just you. We have quite a few clients in this same boat. (One client is migrating to Teams in a couple of weeks for this exact reason.) We have quite a few RIA clients, and because of archiving requirements, this is happening to every single one of them. These aren't poor companies, but Slack is making it really hard to justify the expense anymore. We will have quite a few companies dump them when renewal comes around.