Implementing desktop extension for a multi instance uwp app

I followed this article to add desktop extension for my uwp app which is multi-instance. But I am getting deployment errors:

Deployment Error Prompt

Error DEP0700: Registration of the app failed. [0x80073CF6] AppxManifest.xml(79,10): error 0x80080204: Cannot register the package because EntryPoint must be specified when SupportsMultipleInstances is true.

If I provide entrypoint same as my uwp app(UWP.App in this case) although there is no deployment errors but the appserviceconnection fails with this message:

App not available

Any suggestion how I should go about this??

[Edit]

I made an out-proc AppService as described in this article and started it from full trust process following the same procedure in the article. But I can't seem to find any way to capture its instance from my uwp app. Any help??

Create out-of-proc appservice as described here. Disable multi-instance for out-of-proc service. For each instance of uwp app create a new service. Create a static field in the background task class to store the appservice for desktop extension and initialize it when you create appservice from the desktop extension. Then you can pass messages from uwp app instances to out-of-proc appservice and then from appservice to desktop extension.