Following the official guide, you'll bump into the following error:
$ sudo zypper ref
Repository 'Google-Chrome' is up to date.
Retrieving repository 'Yarn' metadata --------------------------------------------------------------------------------------------------------------------------------------------------------------------------[\]
Warning: File 'repomd.xml' from repository 'Yarn' is signed with an unknown key '9CBBB5586963F07F'.
Note: Signing data enables the recipient to verify that no modifications occurred after the data
were signed. Accepting data with no, wrong or unknown signature can lead to a corrupted system