Hi,
Fun fact: given that database [sbdb] is a secondary replica database on the instance you are in, without ApplicationIntent=ReadOnly,
CREATE LOGIN [domain\testuser] FROM WINDOWS WITH DEFAULT_DATABASE=[sbdb], DEFAULT_LANGUAGE=[us_english];
is working
while
ALTER LOGIN [domain\testuser] WITH DEFAULT_DATABASE=[sbdb], DEFAULT_LANGUAGE=[us_english];
doesn't work.
Regards,
bpsauce