MAS is the best way to activate Windows without installing shady things. I activate my VMs with them and used it in the past om bare metal, they're the safest as you can get in terms of activating Windows.

It is the best and safest, you should use it (Used it a few times on various machines to activate)

I've used that script and can confirm it works. I was actually coming into this thread to recommend it. I don't think there is anything nefarious in that script. Or at least I haven't had anything bad happen on the machine I used it on. I suppose someone with more knowledge could look through the script to see if anything looks out of place.