Creating a boot partition

Total linux noob.

I installed ubuntu on a nvme drive.
Later realising I hadn’t cleaned up other drives before installation.
Multiple SSDs had windows boot/recovery partitions from each SSD being a former windows installation and then being a games drive.

Choosing the nvme drive in bios boot selection it automatically goes to the the other SSDs during boot…instead of the nvme and a dual-boot screen on startup, so it thinks I have a dual boot going on when there’s nothing but games+stuff.

I deleted all the boot partitions from every drive, then stupidly tried booting straight into ubuntu even tho I knew that it was borrowing that boot partition from windows to get in there.
Now I’ve deleted all windows boot partitions, linux doesn’t have one.

So I’ve been trying to mount the nvme drive in linux live-usb so I can create grub on the nvme so I can boot.

I can’t mount the nvme in the live-usb so I can install grub on there.
I’ve tried every suggestion and all of them reply errors.

I tried using the repair boot app, it told me that I had to put a flag on the drive using gparted for a grub/boot flag…and I tried fixing the problem in gparted.
Nothing is working, I figured after putting a flag on that drive that the repair boot app was going to see that flag and know where to put a boot partition.

Every single post I’ve seen has some convoluted problem.
Nothing works that I copy, probably because it’s a different problem.
But I feel I know the problem, I just need to mount the drive so I can install grub on it.
Maybe…yet again total noob so just guessing but I feel like that’s the problem.

I mean I could of probably just installed linux again now properly, but I don’t want to give in to this.

Let us know what commands you are trying to run, and what errors you are getting.

Also post the output of fdisk -l when running the live ISO. Run this as root, which means putting sudo in front of it, so sudo fdisk -l or switch user to root then run it.

It is not a bad idea to unplug every non-needed drive when installing an OS or messing with partitions.

To switch to root you probably need to create a password for the root user. Run sudo passwd root then input your chosen password twice. Then you can run su to Switch User, which defaults to root if you do not type in another username, so su root also would work.