I have spent weeks of my life trying to get windows packaging to work. Twice with APPX, twice with MSIX. Mostly with greenfield C# apps, sometimes with existing WPF apps. Every year I think: surely it'll work now, they just published another blog post touting the new features? No. Every time I run into something that's not documented how to be done, something that's not implemented, or something that's broken, often with a detailed bug report that nobody at Microsoft has bothered responding to (e.g. [0] one of
many).
Windows is in maintenance mode. Nothing new and substantial they create will ever get to a working state, they just don't have the resources. I have given up.
[0]: https://github.com/microsoft/microsoft-ui-xaml/issues/8141