OWC Aura SSD Install: 21.5-inch iMac Late 2012 – Early 2013 - YouTube
Apple iMac 2013 (Late) 21.5-inch (iMac 14,3) SSD ,Ram & OSX Upgrades - ZD Laptop Service Centre
iMac Late 2013 21.5 SSD Upgrade - YouTube
Apple iMac 21.5” SSD Upgrade (2013-2015) HDD To Solid State Drive (SATA) | Step By Step - YouTube
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