I located the issue. My project uses SQL authentication, as I already mentioned, but if you look at my connection string, there is no SQL user ID.
In the absence of a user ID, Entity Framework will by default utilize the local client user ID.
I am unable to connect since the latter is qualified in the remote domain but the local client is not.
By using this setting, you have activated Windows authentication (on).
Adjust it to
or you can completely get rid of that field.
2 hours spent looking for bugs on a previous project. this is the 19-zzz