Which NVMe M.2 2TB SSDs are compatible with 2017 iMac 27" (18,3)?

I personally don’t install them in iMac’s as its so difficult to get to them. If you must find a cheaper solution I would just swap out the HDD for a SSD and call it a day.

The reason I don’t instal M.2 SSD’s in Mac’s as the fact they just don’t hold up! Presently Catalina seams to mess up when it hits one. I just did three systems people encountered problems upgrading their macOS, had to replace all three of the M.2 SSD’s with their adapters to real Apple SSD’s or in one case the OWC SSD.

Here’s a good reference: The Ultimate Guide to Apple’s Proprietary SSDs. As an option look at the OWC or Transcend 3rd party SSD’s. which are designed to for your system.