Although Godot gained C# support with the release of Godot 3.0, it was missing support for key platforms, specifically mobile and browsers. News from the Godot website indicates that Godot will receive C# support on the Android platform starting with Godot 3.2, thanks in a large part to a funding grant by Microsoft.
From the news entry by Ignacio Roldán Etcheverry:
Today I'm glad to announce we've finally made it happen. Godot 3.2 will ship with support for exporting C# games to the Android platform.
The process of exporting a game for Android with C# is the same as it would be if you were using GDScript. Godot will make sure to add all the assemblies and dependencies to the exported APK. No extra steps are required from you.
It supports all target ABIs Godot does (
x86_64). Currently, we only use JITed code, with AOT support coming in the future.
If you want to try Android C# support with Godot you need to build it yourself until the 3.2 release occurs. Details of building with Mono support are available here.
They also discuss the future plans:
The next step in the roadmap is integration with the MonoDevelop IDE. More details will come in the next devblog, in a bit less than a month. You can expect much awaited features like debugging as well as better experience for opening files with this IDE (currently we use the command line with bad results). Thanks to the editor re-write, this will be a much easier task.
If you're wondering about support for WebAssembly and iOS or integration with Visual Studio and VS Code, don't fear. Those are all on the roadmap. You can expect to hear more about them in the future.
Learn more in the video below.