Skyfly, I registered my equipment with my country’s RME distributor.
It was easy to do on the distributor’s website, I just filled out a form under "support".
https://www.synthax.co.uk/rme-warranty
Different country’s distributors sometimes offer improved warrantee conditions as RME reliability warrants such confidence.
The thing is if you have a problem, your countries RME distributor is really your first port of call to help sort out any issues that might arise, they are RME experts.
Look for your countries RME distributors website under "support" - "registration".