Contrary to popular belief, you can run many different off-the-shelf brand NVMe drives on all of the NVMe-fitted Intel Macs. All you need is a passive adapter. My 2017 MacBook Air has a 250GB WD Blue SN570 in it.
Not all Intel Macs. Only those without T2 chip, as T2 acts as the storage controller.
Rohansi
And all of the Apple Silicon Macs have them soldered on or use a proprietary module. They make way too much from storage upgrades to include an M.2 slot.
daneel_wOP
The on-board storage of their MacBooks is as much, if not more, driven by their design vision. They didn't make these things record thin to get an excuse to use surface-mounted RAM and storage. I don't agree with it, but I understand it.
https://forums.macrumors.com/threads/upgrading-2013-2015-mac...