Pretty much, you can't - if nothing else it's pretty simple to spoof the User Agent Strings which are what tells you the capabilities:
How to Change Your Browser’s User Agent Without Installing Any Extensions[
^]
I changed mine to LCARS for a while, just to see is any systems really look too closely...
And Chrome is phasing them out anyway as they reveal too much "personal information":
Google to phase out user-agent strings in Chrome | ZDNet[
^] so any solution you create now based on them will have a very short life span!
In addition, you would have to decide "what is a PC and what isn't?"
Win 8 and 10 ran on MS phones (all ten they sold, IIRC), and my Surface is a Tablet some of the time, and it runs Win10 as well.
What about VMs? Do they count? VirtualBox runs on MAC, and WINE will run Windows on an Android device ...