They key word here is "their". Not your interest, theirs.

Legitimate interests may be those that allow the functionality of the service as such (eg. technical details), all others are blocked or fed with false data to make it clear to them, where they can introduce these "legitimate interests" with Vaseline.

fair enough, i have a legitimate interest in always blocking trackers and advertisements in every device i own too

Do not question, just obey.

Legitimate Interest is an attempt at working around the GDPR using a loophole in the ruling meant to permit processing of data in situations such as when a business has a trading relationship with a client.

However the legal clarification from the EU Commission says: "Your company/organisation must also check that by pursuing its legitimate interests the rights and freedoms of those individuals are not seriously impacted, otherwise your company/organisation cannot rely on grounds of legitimate interest as a justification for processing the data and another legal ground must be found." (see here) and there is a "right to privacy" in EU law.

So supposedly that nearly endless list of "partners" (read: advert providers, trackers and other assorted businesses who make money from breaking people's privacy) cannot use legitimate interest to track you as that would break your right to privacy.

That said, in practice they probably do, and until they get fined hard they'll keep on doing it, so as others said, don't used a Chrome-based browser and use a good Ad Blocker add-on.

Just autowipe cookies on pageloads. Use fast rotating vpn, tunnel through tor twice, run computer in ram only, remove all storage devices.

Use Firefox (or a hardened fork like Mull) with uBlock Origin and you'll never see this BS again

It’s their interest, not yours.

Your honor, it was not a rape, it was my legitimate interest in sex.