I find .NET Core (particularly ASP.NET Core with F# via Giraffe - https://github.com/giraffe-fsharp/Giraffe) extremely good since Microsoft went all open source. I have multiple backends running in a GCloud Kubernetes cluster and develop all my stuff from a non Windows environment. Couldn't be more happy and the speed of ASP.NET Core with Giraffe is fantastic (~100K r/s).