We used to have a domain (foo) but the domain controller machine has been dead for a long time.
I am logged into my Windows 10 workstation as foo\mike and would like to add foo\mike to a local group which already has foo\Administrator as a user.
It is not possible to select foo\mike as an additional user for this local group because it is "not from a domain listed in the Select Location dialogue box". This of course makes sense.
Is it possible to add this domain user to the local group somehow or is my only option to build a domain controller so the foo domain exists again (and even then I do not know if it would work to set up foo\mike in the new AD)?