Github is actively merging features of Azure DevOps and they plan to merge the two eventually, also business model changes, integration with VS Code, Azure, etc.
Github is actively within Microsoft ecosystem and all for the better of both sides from my experience.
Xamarin was crap before the Microsoft acquisition, it was improving at great pace afterwards and it's pretty integrated into .NET standard story (but still crap last time I used it 3 years ago) - I don't even see how you could say anything like they left them alone, feels more like they got rolled up in to .NET devision, again for the better of both (Mono was still the only solution for some scenarios until very recently even outside of mobile)
Github is actively within Microsoft ecosystem and all for the better of both sides from my experience.
Xamarin was crap before the Microsoft acquisition, it was improving at great pace afterwards and it's pretty integrated into .NET standard story (but still crap last time I used it 3 years ago) - I don't even see how you could say anything like they left them alone, feels more like they got rolled up in to .NET devision, again for the better of both (Mono was still the only solution for some scenarios until very recently even outside of mobile)