OWC 32GB (2 x 16GB) PC21300 DDR4 2666MHz SO-DIMMs Memory, Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs, (OWC2666DDR4S32P) at Amazon.com
8GB DDR4 - DDR4 RAM for Dekstops - 2666MHz DIMM - VisionTek | Dell USA
Compatible motherboards with Gigabyte 2666MHz DDR4 16GB (2x8GB) - Pangoly