I like Firefish, I am on a Firefish instance myself, and I feel really good about it. It’s fun to use and it federates with Mastodon most of the time, and with Misskey some of the time. Unfortunately, microblogging on the fediverse is not as straightforward as forums on the fediverse, as they’re a lot more fragmented and there are 5 or 6 different platforms instead of 2 like we have here.
Private trackers exist and some have frequent signup windows.