Curiously enough, influencers' pages are actually ad pages, because some of them get paid to promote products. But of course they won't be paying you. Celebs might also promote their latest movie/song/coffee machine/perfume cooperation. Are these ads?

So the "no ads" model falls apart there.

I wonder if a non-targetted ad could be considered privacy-preserving. Then of course I thought but I'd want some targetting, e.g. by country, because for example having an ad for a spa in Helsinki would be quite irrelevant for users in Bangladesh... then how about by age-range, or gender, etc.

At least I'd welcome when the app transparently says e.g. "You're seeing this ad because it's targetting males over 40 with the geo-ip location of Europe".

Yes - I saw that this is precisely what was on your mind when you asked about it. Typically celebrities and influencers would pull other people too into platform (well, it could be also visible in revenue).

These are some of the reasons why it is a hard problem.