Referring to my previous post, perhaps it is not in XCode you need to set the setting which allows your app to be downloaded on the Mac M1 through the AppStore but rather the web interface for the app store when you publish the app. I say that because initially all apps could be downloaded but then app-makers such as Netflix didn't want their iOS apps to be used on the Mac M1 so Apple changed that.
If you enable this option, then you will also most likely resolve the problem of the app being shown up as a not certified developer.