Microsoft seems like "a house divided" when it comes to opening .NET. They open source the core language, but have different proprietary dev tools (debugging for one) you need to pay for.
https://isdotnetopen.com/ goes over these in more detail, but I'd rather use an ecosystem where I don't have to worry things will be progressively locked down in the future.
https://isdotnetopen.com/ goes over these in more detail, but I'd rather use an ecosystem where I don't have to worry things will be progressively locked down in the future.