I find getting/keeping on top of all discussions is more a problem of raw volume than the software. Small discord servers are easy to keep up on. With large ones, like most popular community servers, I don't bother trying, and instead pick a few channels to focus on. But that was true old-school forums, too. I recommend disabling most notifications.
For a new community, I don't know, maybe one of the nice XMPP servers. That's more viable than average for a tech community in particular. They're trying to make it happen again.
https://xmpp.org/software/?category=servers&cscore=advanced&csim=advanced&csmobile=advanced&csweb=advanced&csav=core I remember hearing good things about Prosody as a relatively turn-key setup, but ejabberd is obviously one of the classics. Someday I'll test-drive a couple of them..m