Memory Upgrades for 2019-2020 iMac 27-Inch - Up to 128GB
2019 5K iMac RAM Upgrade Guide - YouTube
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 RAM in the (Mid 2017) 5K iMac & save $$$! - YouTube