>So maybe the ones you saw are scams as well

I bought one already so I know it's not a scam. Scams usually communicate badly and they don't want to meet you in a public space (like a McDonald's with free wifi)

Obviously ymmv

>Anyway, I wouldn't spend 400 Euros on a used mac with no warranty.

This I agree with. I still prefer Thinkpads too but these M1s are also pretty good in almost every sense except for repairability