Amazon.com: v-Color 32GB(2x16GB) 2666MHz ddr4 Compatible for iMac Retina 5K, 27-inch, 2019 and iMac Retina 5K, 27-inch, 2020 Non ecc SODIMM Mac Memory Ram Upgrade pc4-21300 CL19 260-pin 1.2V (TN416G26D819K-VC) : Everything
Adamanta 32GB (2x16GB) Memory Upgrade for 2020 Apple iMac 27" w/Retina 5K Display, 2019 Apple iMac 27" w/Retina 5K Display, 2018 Apple Mac Mini DDR4 2666Mhz PC4-21300 SODIMM 2Rx8 CL19 1.2v DRAM
How to Install Ram on the 2019 27 inch iMac and which Ram to Buy? - YouTube