Do we talk about “alternative” browsers? No, because there (still) is no “official” one, there’s (still) no single governing entity. Just standard protocols anyone is free to implement and join the party. See Mastodon – there is a kind of official web client and a kind of official native app and a kind of official default instance, but everyone is mostly free to do whatever they want. There are many great instances and clients. Not alternative clients – just clients. The difference being that an alternative client can be one day just cut off.