> Speaking of which, the memo implies that “significance” in this context is interpreted as being relative to the population of the UK, not relative to the user base of the service. We have seen risk assessments that take the other interpretation and consider their UK user base to be “significant” because it makes up a large portion of their overall user base, but the advice we received suggests we should not use this interpretation.

Interesting - this implies that the vast majority of niche communities are not considered to be in scope, so long as they're not on a service like Discord I guess.