Amazon.com: Valley Of The Sun Graphics Video Card GPU Replacement for Apple iMac Mid-2010 A1311 Core i3 3.06 MC508LL/A MC508 21.5 Inch Desktop Computer, ATI Radeon HD 4670 GDDR3 256MB, MXM VGA
Apple Outlines Metal-Capable Cards Compatible With macOS Mojave on 2010 and 2012 Mac Pro Models - MacRumors
Amazon.com: Valley Of The Sun Graphics Video Card GPU Replacement for Apple iMac Mid-2010 A1311 Core i3 3.06 MC508LL/A MC508 21.5 Inch Desktop Computer, ATI Radeon HD 4670 GDDR3 256MB, MXM VGA
How to Upgrade/Replace GPU Graphics Card on Mid-2011 21.5" iMac - YouTube