Interesting in this context is completely divorced from morally good/bad. Could be any group from any area at any time in history. I’ll start with a few, followers of the cult of pythagoras, contemporary black Hebrew Israelites, antiracist skinheads and the Amish (neo-luddites in general). Don’t be racist or a prick to other people discussing.
The word interesting is doing a lot of work here.
On one hand flat earthers are very interesting. Stupid the stupidest but interesting.
On the other hand it’d be better if there were no flat earthers at all for them to be interesting in the first place.