AppService isn't exposed after packaging to .msix

I have an Avalonia app targeting Windows desktop (thus, WinUI3 app).
From that project, I reference a UWP Runtime Component which handles calls to an AppService

Lastly, using a WAP project, I package the app into a .msix package, which declares in its manifest the AppService endpoint.

Everything works well when deploying the WAP project from Visual Studio (both in Debug and Release modes), but when I publish it using Publish -> Create app packages... and I then install it in the PC, the AppService starts to return AppUnavailable status when my test client tries to connect.

I have already checked namings are ok. What could it be?

Here there's a minimum reproducible example. Cloning it and deploying it from Visual Studio, and then installing it from its .msix package should denote that it works in the first scenario and it stops working in the second one.

Thanks a lot in advance for any help you can provide me