Try using the chroot tool in the live ISO, or, even better:
you have to mount exactly /dev/nvme0n1p2 onto /mnt/broken and /dev/nvme0n1p1 should be your $esp later on.
By-the-way, I noticed only now. This was not meant to be run!
First you chroot, then you reinstall grub. And if you have troubles, you can pipe output from terminal to the internet in the suggested way (but from a live iso, it should be better to copy text from chroot terminal and past from the browser of the live iso into the forum).