Making an android app with c#

Build Mobile, Desktop and WebAssembly apps with C# and XAML.

Uno - an alternative to Avalonia, but not as popular.

Create iOS, Android and Mac apps in C#

Xamarin - Basically an older version of MAUI. I would advise against creating new projects on Xamarin since MAUI is supposed to render it obsolete.

A multi-platform .NET UI framework

Avalonia- Basically a cross-platform version of WPF. Far more mature than MAUI and is very well-respected. (My personal recommendation).