Unless things have changed recently (last year or so), the SDF Mastodon servers are really slow and terrible at federating. They even had an incident where the servers failed, everyone lost their posts and had to start over again. Downtime was terrible.

SDF welcomed everyone openly during the initial Mastodon waves, so it was all very Eternal September.

If you're joining to make a spare account to participate with SDF people, awesome! But if you want it as your identity for all of Fedi, I think that would be a bad experience. I ended up getting my own MastoHost account for a while and it was a vastly better experience, until I burned out on Fedi.

SDF is a super fun place to experiment with Gopher though. I absolutely recommend getting your own Gopherhole on SDF. It's like the old Geocities days but in ASCII. (And make sure you grab Lagrange as your GUI Gopher / Gemini client. I liked Phetch as my terminal Gopher client.)

Which one? There are two instances, one for members, and one for everyone.