The MDrivenServerOverride.xml file is placed in app_data of the turnkey server 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 regretfully incompatible. You best bet is to turn in 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>