I think the raw text inside Facebook groups is at least as valuable as Reddit data. Even if demographics data is restricted under European law, the raw text of people interacting is quite valuable.
That ignores all the user groups that are on Facebook. From apartment communities aka Nextdoor to grief support counseling to the mindfulness therapy groups, there’s a wealth of user comments a tad bit higher than Uncle John’s racist rants.
facebooks downfall will be their lock in. every other social media platform lets you view a public profile, discussion groups etc. it's all locked inside facebook.