C# is a pretty underrated language. I've worked with JS, Java, C++, Perl and I've always preferred to use C# for personal projects.

async/await - C# is the ONLY language which gets this right. Javascript has it now but you need to be use libraries which support it too, which are hard to find. Kotlin has coroutines but Java base library doesn't have support for coroutines so you can't use it all the way through and create a chain of all async functions. Once you use async/await it's hard to go back, since the code is as easy to write as synchronous code.

Then you have proper support for generics(unlike Java which has type erasure), LINQ queries and an amazing IDE which is visual studio.

I’ve always liked C#. But official support outside Windows is only very recent.

And .NET is still very much Microsoft’s baby. Unlike an independent language like C or JS or Rust, MS could pull the rug out at any time.

Yes, Mono. But Mono is an unofficial port of a moving target. They have no control over the direction of .NET.

What you mean? C# is open source. And, here is the location - https://github.com/dotnet/csharplang