I thought the same for the longest time. I blame playing tons of runescape as a kid.

I am an American so mold spelling is definitely what I ran into when referring to the fungus. Runescape is British English, so you used moulds all the time in crafting.

I personally use C# via Visual Studio only so I don’t have too much experience outside of this, but I know Visual Studio Code has a C# extension and VSCodium should also work. If you are set on really not using as much of Microsoft’s products as possible, you will still have to use the dotnet sdk. From the terminal you would then call dotnet such as dotnet new, dotnet build, dotnet run, etc.

https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet

dotnet sdk is open source -> https://github.com/dotnet/sdk