How to add a fast new SSD to your old Mac or MacBook for only $150 - 9to5Mac
iMac (21.5-inch, Late 2013) 1TB SSD Upgrade - NiwTech
How to Upgrade the Main Drive in a 21.5-inch iMac 2012-2015 (iMac13,1 iMac14,1 iMac14,4 iMac16,1) - YouTube
Amazon.com: Sintech M.2 nVME SSD Adapter Card Upgrade Kits,Compatible for MacBook Air(2013-2017 Year) and MacBook PRO(Late 2013-2015 Year,iMac : Electronics
2013 iMac teardowns reveal SSD slots, soldered-in CPU in the 21.5” model | Ars Technica
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
OWC Aura SSD Install: 21.5-inch iMac Late 2012 – Early 2013 - YouTube
DIY SSD upgrade kit for late 2013-2019 iMac|iMac late 2013-2019 SSD with upgrade kit|Flexx Memory|Free UK Delivery