You’ve installed SonarScanner for .NET on your Mac, and when you try to run it you get an error saying you must install .NET?
And you’ve installed .NET with brew?
Getting .NET properly installed is a bit out of scope for us. The assumption is that you don’t need the SonarScanner for .NET until and unless you’re already compiling with .NET.
What I can say, though, is that you should make sure that dotnet is in your $PATH.