.NET Core ran on Linux from version 1.0 on and it was released 2016.
I'd rather use something open like python, go etc. And most people do, there's few Linux apps that use .net. Microsoft didn't even use it for visual studio code.
Did you know that .net is open and python runs a bytecode interpreter?
Don't believe me ? Check how many of the .net docs pages have the relevant banner.
JetBrains Rider is amazing, fyi!