I have just installed a nvme M2 card (Samsung 980 1T PCIe 3.0) on my ASUS Prime B250M-A motherboard that has two NVME M2 slots and managed to install Ubuntu on it. It was seen during install.
But the motherboard won't boot on it. I have to start the bios and manually select the ubuntu disk in some boot list showing up. Then Ubuntu will start, but it's slow to start due to errors. Ubuntu boots faster on my old SATA SSD disk.
The problem is solved. I left the old not working SATA SSD connected. Once I disconnected it, the computer worked as expected. There is apparently a problem with this old SATA disk that was confusing the BIOS.
The symptoms were strange. I could not enter the bios when pressing the del or F2 key. Forcing a boot on the nvme M2 card was slow. There was not POST or error feedback.
Once the old SSD was disconnected, I could enter the bios without problem and the PC would boot really fast.
So, if you encounter a similar problem, like failing to boot on nvme card, the first thing to try is to disconnect all other hard drives and leave only the nvme card. Once I did that, all problems were gone. I then reconnected the hard disks one by one until I found the one causing the problem and it was the old SSD.
