How to Install Memory iMac 27-inch 5K (RAM Crucial 16GB) - YouTube
Install memory in an iMac - Apple Support
How to upgrade the 27-inch 5K iMac (2019) with a massive 128GB of RAM [Video] - 9to5Mac
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
Factory Original 64GB (2x32GB) Memory Upgrade for 2020 & 2019 Apple iMac 27" w/Retina 5K Display & 2018 Apple Mac Mini DDR4 2666Mhz PC4-21300 SODIMM 2Rx8 CL19 1.2v RAM Adamanta at Amazon.com
How to upgrade iMac (2020) RAM and save up to $2000 - 9to5Mac