Earlier quoted context omitted.
When was the last time your passport was copied in Europe? I don't think that this is still legal under the GDPR.
All KYC processes require copying in Europe. There's nothing that's blanket illegal under GDPR. If you have consent you can collect and store whatever you want.
If hotel staff says "Ok, last step we need to do to check you in is to copy your passport" that would probably neither count as freely given consent nor as keeping data collection to a minimum.
And KYC also does not mean you have to copy the passport of a person.