There is solution for connecting VS2019 to TFS 2010 similar to our situation,
How to connect Visual Studio 2019 to TFS?
In our case the servers and computers are on a local network, intentionally disconnected from the Internet.
VS seems to want the server hosted as an Azure DevOps Server.
Is there any way to connect VS2019 to a local TFS server without the Internet?
In the "Connect to a Project" dialog there are no hosted repositories listed for my account (as expected).
When I attempt to add the TFS server in the "Connect to a Project" dialog, the error is:
Server was not added.
HTTP code 504: Gateway Timeout