Yeah that is a really tricky thing, even if those communities decide to go “we’re moving to ______”, they will inevitably be leaving behind a lot of their userbase, and be giving up a large amount of SEO and discoverability. The large number of users is what gave reddit its value, so I can only hope that groups that might disperse find a central place again. I definitely don’t envy the position this leaves moderators in rn.
Absolutely - discord is probably one of the worst choices to host a “discussion board” type page for those reasons. They are well on the path of enshittification too with all the bloaty unnecessary features they’ve added over the years.