This was a big step in the right direction. Unfortunately it didn't seem to work for the latest alpha 2019.2.0a11, or the 2019.1.0f1. I fixed up the alpha search path, and added more that I'd recently discovered for f and b builds. Would love if you'd try out these changes @StephenHodgson and report here.

I've also modified the search to now look for any matching installer templates as well (the a/b don't have a link to UnitySetup with a version in the url) so I've dropped the special case for searching for the builtin_shaders. I'd like @Ziugy to review and try this out as well.

I did test my new changes with Get-OperatingSystem returning both Windows and Mac.

If @StephenHodgson and @Ziugy like these changes we'll move them in. If I didn't change the code I would have approved it myself. =)