What does Mono have to do with any of this?
Mono is not a Microsoft product. Microsoft would like to take control over it, have been trying to for a decade and a half now, but it's open-source. No one owns it.
Try to stay with me here....
Microsoft "de-supported" Visual Basic 6, and stopped (for a while) even distributing the parts which would allow software written in VB6 to run on their newer OS releases. Microsoft's plan was to "encourage adoption" of the new VB.Net language and its twin, C#.
The EU raised hell, because in one fell swoop Microsoft had rendered worthless many tens billions of dollars of investment in software written in VB6. By "raised hell" I mean that they refused to use the new Microsoft products unless Microsoft registered their designs as open standards.
Microsoft did exactly that, registering the design of the CLR and the libraries with the ECMA.
Novell reacted by hiring a team of programmers to make an open-source version of the CLR, libraries and compiler, known as the Mono project. (The principal programmer explained the name Mono: "'Mono' is Spanish for 'monkey'. I like monkeys.")
Microsoft began desperately trying to put that genie back into the bottle, at one point even trying to buy Novell. In the mean time, Mono was ported to... well, to just about everything. It runs on about as many platforms as does Python.
Xamarin released a set of programming tools for writing C# code, to run on Android, using the Mono CLR. Microsoft then bought Xamarin and declared victory: "We now own Mono." And now, "We can converge our forks of .Net and Mono into a single product line."
Er, no. Someone went off their meds. Mono is still Mono, doesn't belong to Microsoft, isn't under Microsoft's control except in their demented dreams.
And that's a damn' good thing, as I've used Mono to run C# programs on Linux for something like ten years. I want it to keep working properly.
How do I know all this? I was using both systems, including the Android version, while all this was unfolding.