With a 2010 iMac I would be able to connect an HDMI to mini DisplayPort cable from a GPU to the iMac and have the iMac act a monitor using Target Display Mode. However, after some research I found that the 2011 iMac cannot do this and its Target Display Mode only works if you are connecting from a Thunderbolt device.
Is there any cable or converter or even a GPU with a Thunderbolt-output that I can use to get around this?