I use OpenCore, on my 2010 27" iMac of all things. Needed to enable target display mode and native brightness control on the new K610m GPU. So in essence, my actual Macintosh is now a Hackintosh in Apple's eyes.
If you have a 2010 or 2011 iMac with a dead GPU btw, check out this thread on the MacRumors forum: https://forums.macrumors.com/threads/2011-imac-graphics-card...