Many thanks for the hint @764287, at least I get a response
restic init -r s3:s3.us-west-000.backblazeb2.com/XXXXX
enter password for new repository:
enter password again:
Fatal: create key in repository at s3:s3.us-west-000.backblazeb2.com/papanito-private-backup/test failed: client.PutObject: not entitled
Looks like I miss some permissions, even so the key looks fine
Ok there was something wrong with my key, created a new one and looks fine using s3. b2 option also works, once the key was fixed. Will feed this back to the issues