Firstly, I think there are a lot of people on the fringe of the extremist groups. Maybe they are only in a "concerned parents" group who talk about vaccines, but it's an on-ramp.

Secondly, I think there are methodological issues with that analysis. Measuring by App Store categories is hard to do accurately, only presents a snapshot in time, its numbers that fluctuate a lot, and it only represents new user acquisition, not active user growth. I wouldn't trust this number at all without more information. Anecdotally, I don't know anyone who uses Telegram, although I do know many people who downloaded it once.

> where do the far-left extremists go

This isn't really something we have a problem with in the UK. I'm sure there are some, but the bulk of our issues are growing far-right, nationalist, and/or authoritarian groups. I don't think a debate over terms is going to be productive, and as this is your third account you might want to be careful with it!