So, I bought a new NVMe drive (WD Blue SN550 500GB) for my older gaming laptop (2015, Asus ROG GL752VW) today, that used a SATA III m.2 as boot drive until now. When inserting the NVMe into the slot and trying to install windows, the drive didn't show up. I afterwards went into the BIOS, where it only showed the disk reader and my HDD.
The manual of the laptop states NVMe support, as well as that some of these were shipped with NVMe drives. My BIOS is the latest version on Asus' website.