The MDrivenServerOverride.xml file is placed in the App_data of the TurnkeyServer and overrides the default server/__MDrivenServer location of the MDrivenServer.

Also, see the HardServerUrl setting for the MDrivenServer:

<root>
  <MDrivenServerOverride MDrivenServerPWD="thepwd">https://TheUrl</MDrivenServerOverride>
</root>

When connecting a server built with .net Core to a server built with .NetFramework, the SignalR versions are regrettably incompatible. Your best bet is to turn it off like this:

<MDrivenServerOverride MDrivenServerPWD="somepwd" SkipSignalR="true">https://SomeServer</MDrivenServerOverride>

When connecting a server to a modlr file in order to quickly prototype:

<MDrivenServerOverride PrototypeWithMDrivenDesignerInPath="c:\temp\dummy.modlr" CopyAssetsTKOnStart="True"></MDrivenServerOverride>

You can also instruct the TurnkeyServer to grasp the CodeDress from a specific path. Read more here: Turnkey debug