I recently purchased 2011 21.5 iMac (Mid-2011) and I'm obsessed. : r/mac
64GB 4X16GB DDR3-1600 NEMIX RAM Memory for Apple iMac Late 2015 27" Retina 5K - Newegg.com
Apple says it's vintage. It's a 21.5 in 2011 iMac w/ 32GB ram, 4GB AMD wx4150, 512GB and 1TB internal SSDs on a 2nd primary 2011 Thunderbolt Display running Ubuntu. Playing some Apex Legends right now : r/retrobattlestations
Install memory in an iMac - Apple Support
HOW TO: Upgrade The RAM to 32GB on a Mid-2011 21.5inch iMac - YouTube
21.5" iMac (Mid 2011) Model ID:iMac12,1 - TransIntl
iMac RAM Models 11.3 (i5 and i7 only) to 12.2 (8GBx4) | MacMemory.com