New 21.5-inch iMac least repairable yet due to lack of RAM, hard drive upgradability - 9to5Mac
Install memory in an iMac - Apple Support
Apple iMac 5K Retina 27" Desktop - 3.2GHz Quad-Core i5 - 16GB RAM - 1T – The Refurbished Apple Store
Install memory in an iMac - Apple Support
How to Install Memory Into a 27-Inch Apple iMac (Late 2015 - 2020) iMac17,1 iMac18,3 iMac19,1 - YouTube
iMac Retina 5K: Memory upgrade (RAM)
OWC 8GB (2 x 4GB) PC12800 DDR3L 1600MHz SO-DIMMs Memory Compatible with 2011-2015 iMac, 2011-12 Mac Mini, and 2011-2012 MacBook Pro (Non-Retina Display) Models (OWC1600DDR3S08S) at Amazon.com