macOS issues
App menu
App menu shows About Avalonia menu item
This means that your application most likely does not specify a menu. On startup, Avalonia creates the default menu items for an application and automatically adds the About Avalonia item when no menu has been configured. This can be resolved by adding one to your App.xaml:
<Application xmlns="https://github.com/avaloniaui"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:RoadCaptain.App.RouteBuilder"
x:Class="RoadCaptain.App.RouteBuilder.App">
<NativeMenu.Menu>
<NativeMenu>
<NativeMenuItem Header="About MyApp" Click="AboutMenuItem_OnClick" />
</NativeMenu>
</NativeMenu.Menu>
</Application>
The rest of the macOS default menu items will still be generated by Avalonia.
Application name in menu bar does not match
When you run an app from a bundle the name for the app that is shown in the menu bar is taken from the Info.plist in the bundle instead of the Name property in App.xaml.
If the names do not match, verify that the values for CFBundleName, CFBundleDisplayName and the Name property are the same.
Note that CFBundleName is limited to 15 characters, if your application name is longer you must set CFBundleDisplayName.
See Application name and identity for full details on where macOS reads the app name from.