Hey Ryan
I had a similar issue when moving my personal repos from DevOps to GitHub.
I’m not sure if this simply means “Don’t use this for C# at all” or “we don’t support Windows…"
No support for any flavour of .NET in GitHub Actions as yet.
There are a few custom GitHub Action tasks that can run the scan for you in a Docker Container and report a quality gate and do branch/PR analysis for you. The one I ended up going with was this: GitHub - highbyte/sonarscan-dotnet: GitHub Action SonarCloud/SonarQube scanner for .NET 7/6/5 and .NET Core applications with pull request decoration support. My implementation: https://github.com/KrylixZA/Shared-WebApi-Core/blob/master/.github/workflows/ci.yml#L67
Unfortunately there is nothing official yet but these alternatives seem to work okay. It does mean you do a double build as you can’t use the Docker container to build and publish NuGet packages or push to a Docker registry or anything like that. So a full solution from Sonar Source wouldn’t go amiss and I’m sure it’s in the pipeline.