[GordonS]

You don't even have to use Windows - Linux/MacOS and .NET Core is a combo that works really well.

For OSS, I really like Github, and honestly even moreso since the Microsoft purchase, since there has been some actual progress.

For non-OSS though, I favour Azure DevOps over Github (despite the silly name) - they have a very generous free plan that includes pricing repos and build time on Windows, Linux and MacOS build agents. The CI/CD side of it really is fantastic - I've used Travis, Appveyor, GitLab and Jenkins, but Azure DevOps is just so much more capable.

With Microsoft buying Github, I'm actually kind of worried about what is going going to happen with Azure DevOps - it really is a great platform, and I hope Microsoft don't end up replacing it with Github...