Yep! And they have different styling & feature sets that some may prefer, like Firefish has full text search & quoting posts unlike Mastodon for a super basic yet big difference.
There’s also a bunch of other features I haven’t dug into much that are interesting, like “antennae” for following words/hashtags and widgets for a variety of things. I don’t know how well they all work, but overall it’s aiming to be much more robust than Mastodon.