Buying used Macbook Pro, checking if it's linked to previous owner

If I buy a used Macbook Pro from 2015, how do I check if it is registered to the seller, i.e. linked to his AppleID? I checked through the "Check coverage" Apple support site (Check coverage), and the first point is a green check mark, the remaining two are yellow exclamation marks saying that it has expired. How is this to be understood?

Also, what other things do I need to check to make sure that I do not end up with a Macbook linked to someone else? I want to be able to link it to my own ID as if it were new. I've read that one of these things is that "Find my mac" is deactivated, how can this be verified?

There is no link you can’t undo or clear to an old account other than Activation Lock and a firmware password.

• https://support.apple.com/en-us/HT208987
• https://support.apple.com/en-us/HT204455

You need the owner to give you a bill of sale and cooperate with both the above procedures. Get their support in writing or escrow your funds till you can validate things.

All the other steps for preparing a machine for sale protect the seller and don’t inhibit your full use and control of the Mac when you take possession of it. You will want to erase the Mac and be sure you never lose your firmware password since you can’t bring the original proof of purchase and prove the Mac is yours to have Apple unlock it.

• https://support.apple.com/en-us/HT201065