[jasikpark]

Discord, is great, works well with groups up to 40,000 and can work as a simple IM messenger, though you still have everything from the group message features as in Slack.

[donbindner]

Try to go back and delete old conversations.... Discord really falls down there.

[asherdavidson]

They have decent search at least. Lots of filters you can customize. It feels a little janky to use though.