Mono was largely folded into CoreCLR a couple releases ago and part of that infrastructure is used to support some targets like mobile and WebAssembly.
[disclosure: I work on Mono at Microsoft.]
Re:What's new in C# for Godot 4.0
by jackmott42 on Sunday February 26, 2023 @12:28PM
(#34947339)
Yet Godot manages it, with a volunteer team and a better overall user experience.
And I think .NET6 supports mobile now?