As far as finding any options relating to M.2 of NVME drives, I would suggest checking again under the Advanced or maybe Boot sections in your BIOS. The manufacturers tend to put them under there, whereas you can just skip the other menus.
reset BIOS to defaults, then search every option/sub-option in BIOS for enable/disable NVME M.2, etc... ; certainly, until we can find it in the BIOS, it will not show elsewhere...
As far as finding any options relating to M.2 of NVME drives, I would suggest checking again under the Advanced or maybe Boot sections in your BIOS. The manufacturers tend to put them under there, whereas you can just skip the other menus.