Secondary login prompt fails during installation of a network printer under Windows

When installing a network printer on a Windows 11 PC (the printer is shared on a Windows 10 PC on my LAN), I get a two login prompts. On the first login, when I connect to the remote computer it works fine with .admin as user name:

However, the second login doesn’t work. It doesn’t accept .admin as user name:

Just using admin tells me to overwrite existing credentials:

When I click yes, it just tells me the credentials are not correct:

How can I enter my credentials?

Note: using computernameadmin and admin@computername and 192.168.178.30admin has the same result as using admin

Note: Using the “connect” dialog has the same problem: