Benjamin Eberlei wrote a post on why and how he got rid of Slack in his company.

We have moved away from Slack at Tideways over the last three months, because I found Slack is already annoying, even with just a four person team (plus the occasional freelancer). For me, it disrupts deep work phases and knowledge lost in the depth of chat history.

https://beberlei.de/2018/10/28/unslacking_tideways_company.html