You can go to https://groups.qoto.org and register for a group. But be sure to read the about/more page first to understand how it works! https://groups.qoto.org/about/more
Anyway, as far as I know this is the first time the fediverse has had an open, managed group server.
QOTO also has the group directory. Attached is what the group directory, and a group timeline looks like on QOTO, but we did some streamlining, your client may render groups differently and most wont have the directory, which is a federated list of active groups.
Anyway, anyone who wants a group, go sign up for one! Its open now!
Sorry I forgot to address the second part of your question.. Yes its like guppe in th sense that it basically is a group actor (a thing in activity pub), and as such its reboosts are equivalent to group posts.
The difference between groups.qoto.org and guppe, however, is that groups only has a group exist after someone registers it, and the person who registers it, owns it, and must keep it active (even if only they post in it).
Furthermore the owner gets the ability to moderate it in several ways that arent relevant to guppe, for example a owner can make a group follower only, or it can mute, silence or block a user or even a domain. So unlike guppe the groups.qoto.org site lets you created managed / moderated groups.
QOTO: Question Others to Teach Ourselves
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Hate speech and harassment strictly forbidden.