How can a platform - in general, not just meta - provide a “free” service, without monetizing it with targeted advertising?
One option would be contextual advertising, rather than advertising based on tracking the user.
(Contextual, as in: if you're looking at a Formula 1 community, you might be interested in car-related products.)
They actually did:
Unfortunately, that didn't help. So now they'll have to find out what's causing this, and then see if they can fix it.