When I try to debug my app, it throws the error but compiles successfully when Release is selected.
Applications with custom entry point executables are not supported. Check Executable attribute of the Application element in the package
Following is the Applications tag from the manifest.
<Extensions>
<uap:Extension Category="windows.protocol">
<uap:Protocol Name="myapp" />
</uap:Extension>
</Extensions>
</Application>
Edit:
For some reason stacko is not loading all manifest code so pastebin here: https://pastebin.com/FsFEJZFz
It seems you are trying to launch an exe program from the UWP app.
If it is just an exe file, you could just add the runfulltrust in the manifest file of the UWP application. Make sure to put it in the Extensions
element.
If you need to reference the exe project in your UWP app, you will need to use the Windows App Packaging Project.