My group of friends did the same thing, we moved from group texts (Which became a huge mess) to Slack — not because we like it better than Discord or anything, mostly we're using Slack for work anyway, so it made sense to make a group there.

Works a lot better than group texts, and with better file sharing to boot. We'll still text each other for 1:1 conversations where we're not near a computer.

We'd switch to Discord if Slack's free offering is ever gimped.