Yes there is a guidance, it is called GDPR, it is THE only guidance, just take the concepts, I can give you this link, it is the best I was able to find, it will help understand the GDPR, but for each and every site, owner needs to decide on its own: https://www.youtube.com/watch?v=-stjktAu-7k
The modern web depends on embedding third party content for many reasons, most of which have nothing to do with invading anyone's privacy and many of which are directly in the visitor's interests. It is not helpful to undermine that whole ecosystem and expect everyone to start having formal contracts in place before they can take advantage of any of those services. Nor is it reasonable to expect services offered for free that aren't doing anything shady to take on significant liability and/or other commitments anyway through formal agreements with their users. Why would they do that, instead of just (as obviously quite a few places already have) geoblocking the EU to remove themselves from the scope of the onerous rules?
To the morons (no, it is not insult, it is empirical fact) downvoting me, it is not me, it is GDPR, face the reality, it is not my fault that you are too reluctant to understand it and biting people trying to help you out wont help. Downvoting me wont change GDPR or change anything, you will just loose a valuable source of information as you did just now. Go to the first psychiatrist and it will tell you that a reality will be as it is even if you close your eyes (or shoot the messenger =/).
Don't forget to upvote me, when you figure out I was right and you get a warning/fine.
If you don't want to be banned, you're welcome to email hn@ycombinator.com and give us reason to believe that you'll follow the rules in the future.