2020 5K iMac RAM Upgrade Guide - Save $2100 on 128GB! - YouTube
How to upgrade the RAM on the 27-Inch iMac (2020) | AppleInsider
iMac with Retina 5K Display 2014/2015 Memory Upgrades
CMS 16GB (4X4GB) DDR3 10600 1333MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I3 3.06 21.5-Inch (Mid-2010) - A28 at Amazon.com
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
Amazon.com: OWC 32GB (2 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S32P) : Everything Else
Amazon.com: OWC 64GB (4 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with 27" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S64S) : Everything Else
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET