Material.Avalonia VS FluentAvalonia

Material Design

Avalonia 0.10 (last version) features Microsoft's Fluent Design out the the box. If you prefer Material Design you can use :https://github.com/AvaloniaUtils/material.avalonia

This is what you need : https://github.com/amwx/FluentAvalonia

FluentAvalonia

If you want to have the FluentUI theme you can use https://github.com/amwx/FluentAvalonia. I used this for another project and didnt have any issues.

It's literally not the most basic control for Windows development. That would be something like Window, Button, or TextBlock. If you're only using the basic features of a NavigationView, then you can implement it using a simple ListBox with some minor styling instead. The fully featured NavigationView from UWP has a lot of complexity that most devs won't need. You could also use the implementation from FluentAvalonia

There are many cool custom themes for Avalonia, also default Fluent theme is already very good looking. Try for example this https://github.com/amwx/FluentAvalonia

But, going by the Avalonia route, you have the promising FluentAvalonia project for the Windows 11 look & feel. I was a bit overwhelmed by Avalonia when I tried it but especially for cross-platform projects it's of course a solid contender and probably a strong alternative to MAUI.