is there anything else you did to the machine so it could boot from m2 drive in wifi/2230 slot?
i tried m720q, m920q and p330tiny with 8500t, 9400t, 9500t and 9900t es on last bios and they don't boot from m2 drive in wifi 2230 slot.
it is not detected by bios but test tool available by pressing f10 detects it as a storage. i tried installing esxi to that drive in legacy mode and i did remove everything from boot device list. it does not detect drive as bootable and does not proceed.
I bought two of these adapters to run in my m720q and m920x. Originally I couldn't get either to boot from them (no operating system found error) but both are working now!
Here's what got the machines to boot from the 2230 in the wifi slot:
CSM = Disabled
Boot = Legacy
Boot order = Removed M.2 and network drives from the order, leaving all the USB/other devices (inlc. M.2 Sata). I'm not sure how important this is TBH.
**I can't explain this, but once the machine starts booting from the drive (however you can get it to work), it continued to work after I switched the BIOS back to CSM=Enabled and Boot = UEFI.... Seems like it has some memory of whether or not it will try that device as a boot option.
I'm not certain you have to have Legacy boot either (for those of you with newer generations, e.g. p350). When I did a fresh install of Proxmox from a USB installer onto one of the 2230's it immediately started booting from it without having to change the BIOS. The issue is just getting the machine to recognize it as a boot drive once, then it seems to persist until you remove it.
On a different note - You will need to cut a small notch in the corner of the m.2 adapter as the power button interferes. Learn from my experience, scissors worked better than repeated scoring with a utility knife.