the Facebook case: DMA/ digital markets act. This case is only regarding the choice between personalisation or paying to access the service. Only for really big patients deemed to be gatekeepers. There are only five at the moment: https://digital-markets-act.ec.europa.eu/gatekeepers_en
showing ads that are personalized, or any other things where they use information about you: Gdpr. You have to allow it.
showing you ads that are not personalized: completely legal. Netflix does the same I think. Also Amazon prime.
No.