64GB RAM upgrade kit for 21.5-inch iMAC now offered by OWC - 9to5Mac
New 21.5-inch iMac least repairable yet due to lack of RAM, hard drive upgradability - 9to5Mac
OWC Tears Down iMac Retina 4K, Confirms Memory Is Soldered
Review: 21.5-inch 2012 iMac takes two steps forward, one step back | Ars Technica
Memory RAM Upgrade for Apple iMac 21.5-inch Mid 2011 4GB/8GB DDR3 SODIMM | eBay
I got a FREE 2013 iMac 21.5 with internal upgrades including Samsung evo ssd and 16gigs of ram. Then used open legacy patcher to install Mac OS Venture 13.5 beta. : r/osx