My experience was bad. A lot of servers my friends used didn't take new sign ups so I was forced to pick my own which went offline a few weeks later and I haven't tried using it since because there's no indicator of server quality that I know of and all the servers with a lot of active users are not taking signups. Recommendations from HN would be appreciated.
I use social.coop, and it seems to work well. They have some kind of participatory administration too that I don't know very well.
My recommendation is to find an instance with some kind of governance plan, and hopefully a stable stream of donations. Volunteer instances indeed could go at any time. And of course, if you can, donate to one or a few instances out of good citizenship.
I think it's also worth mentioning there are other services built around ActivityPub as well (and federation). I found friendica pretty good (as a Mastodon/facebook alternative), although I don't use it.
