I think there are certain machines on HTB that more ore less requires a Windows box to test your scripts (or at least it makes your life easier). In particular if you creates more advanced PS scripts, when it comes to hacking SQL server a Windows box is also preferable due to the number of tools available on Windows (the latest version runs on Ubuntu but the management tools doesn’t). And then we have the Active Directory… So I can not understand how a few people in this thread manage without a Windows box.
With that said, I am running a Mac as my ”host” because the build quality of the hardware is superior. I rarely work on OSX though, I have about 5-6 VM’s running with Kali, Ubuntu, Windows. I also have a separate box to crack hashes with dual GPU-cards.
I guess there’s a distinction between “What os do you use?” and “What’s in your lab?”. I have an active MSDN subscription, so I have a number of VMs for windows, and various linux distros, that are ready to spin up, but I don’t feel I’d ever say they are an os that I use. Many of those VMs see less than a hand full of hours of run time per year.