I believe this is the drive Dominic is referring to:
It’s a Gen 5 referenced above, a proprietary SSD that has no adapters or enclosures that I can find.
Between Secure Boot, encryption and proprietary drives, Apple seems to be closing the door on data recovery. A drive or machine failure may well doom all data without a current backup.
Cody Henderson of BeetsTech posted an outstanding guide to Apple SSDs that includes a number of Gen 5 drives at the bottom of his list: The Ultimate Guide to Apple’s Proprietary SSDs