Yes, you are reading that title correctly. After years upon years of receiving unofficial ports of every version of Android and a few other operating systems to boot, the HTC HD2 has just received a working port of Android 6.0, Marshmallow.
Working is a relative term, of course, as pretty much nothing besides the screen, audio or WiFi really works. But it still exists. A senior member of XDA has released the port, which is a build of CM13. If for some insane reason you still have an HD2, head on over to the source link and check out how to get Marshmallow on your piece of hacker history.