Ubuntu Will Not Boot

[spflanze]

I needed to be able to login as root to enable moving my home directory from my SSD to my HDD. I have 2 x TiB SSD, and 2 x 12 TiB HDD. The two SSDs, and the two HDDs, were raided together under zfs, the Ubuntu OS installed. I was able to boot Ubuntu. Then I followed these directions to enable login as root:
https://askubuntu.com/questions/1192471/login-as-root-on-ubuntu-desktop

I created a root password, and edited the two files in accordance with those instructions. When I attempted reboot I was not given an option to boot Ubuntu. It would only boot in EUFI mode. Because this failure correlated perfectly with the edits I made in those two files I thought there was something wrong with the instructions to enable login as root. So I attached the Ubuntu Live USB drive, and booted from there, to undo the edits. But I found that one of the two SSD nvme drives is absent from the directory /dev/disk/by-id. nvme1n1 is not there. Only nvme0n1 is. Has nvme1n1 failed? And if it has, why does the system not boot from the remaining visible SSD?

The two SSDs are: Samsung SSD 980 PRO 2TB

The entire procedure I used to do the installation can be downloaded here:
https://www.mediafire.com/file/2w8mdb96tbzslub/Ubuntu_22.04_Root_on_ZFS_Encryption.odt/file

[spflanze]

The computer taken to a repair shop, where nothing wrong was found. The SSD reappeared in the UEFI, and in the OS when booted from a USB. It is as if driving the computer there fixed it.