I see good points in this comment, even if the analogy of their being like hashtags might be a little off.

gup.pe groups have a 1-word description. Most of them I've been unable to assign a topic to because I didn't know what the word means or it has ambiguous meanings. Most have no posts. So they land in the "unknown" topic.

I always wondered what I would do if someone started posting porn or hate to them. It would be a nightmare. I'd just have to block the group, I suppose.

Frankly, instead of someone creating a gup.pe-like group, I think they ought to create a community in PieFed, MBIN, or Lemmy. gup.pe was an early experiment when there wasn't a threadiverse.

I'm fine without gup.pe or gup.pe replacements.