It's certainly legal to get you to accept advertising, or buy the service.
What they can't do is say "no tracking, no service".
What they can't do is say "no tracking, no service".
If we could turn tracking I to a banned way to earn money from free visitors, I think we’d all be better off. This is not how gdpr works today.
Legitimate interest is things like a legal requirement to maintain PII because of the services offered.