thank you for the reply.
It seems that I’ve figured out where the problem was.
If, in Anvil, I add my credentials and do not set the “Redirect to app origin?” to true.
I get this - google authentication shows “anvil.works” as an apps domain.
However, if I do set the “Redirect to app origin?” to true, I get the domain I wanted (assuming I’ve configured the domains in the google developer console correctly).