At work we had to sponsor a tiny community user group because Slack search on free accounts is really curbed.
If I remember, it is limited to saving 10,000 messages. Steemit Inc sponsored paid licenses of Slack, so we had unlimited history, but it was a limited invite system.
It's a shame all commercial chat option are so freaking expensive.
And the fact we can quickly go through those without noticing shows how much of a fire hose chat systems are - one I am in for retro programming is unfollowable because by the time it is morning in my timezone about a thousand messages have been sent
That's why everyone on Hive uses Discord and the dev channels are on Mattermost.
I haven't seen those, guess they are invite-only or for core devs?
There is a dev Discord, and invite-only Mattermost.