iMac 2013 (and later) with NVME SSD? | MacRumors Forums
Amazon.com: INDMEM NVMe PCIe SSD 256GB 3D TLC NAND Flash Hard Drive Replacement for Mid 2013-2017 MacBook Air, Late 2013 - Mid 2015 MacBook Pro Retina, Late 2013-2017 iMac, 2013 Mac Pro, 2014 Mac Mini : Electronics
Upgrading an older iMac's PCIe SSD: Third-party solutions that save you beaucoup bucks | Macworld
Hard Lesson Learned With Late-2013 Apple Products Containing Lesser Performing 128GB SSDs | The SSD Review