Use your live usb to chroot:
sudo mount /dev/nvme0n1p2 /mnt
sudo mount /dev/nvme0n1p1 /mnt/boot/efi
sudo arch-chroot /mnt
Inside chroot:
pacman -Syu
grub-install --efi-directory=/boot/efi bootloader-id=endeavouros
grub-mkconfig -o /boot/grub/grub.cfg
Reboot.
I have tried something similar. I will give this another shot after work today.
Also, note, if you are using Grub and dracut and when you need to rebuild your initrds you could use:sudo dracut-rebuild
What I am curious about the way grub was updated , I thought you should always run
sudo grub-install
sudo grub-mkconfig -o /boot/grub/grub.cfg
Now I saw that only the last command was used by the OP , could that have messed up the grub bootloader ?
As I understand it, unless first install or a new version of grub is published, you only need the 2nd.
However, it doesn’t hurt to over write the bootloader unnecessarily.
This may have to do or not with OP’s issue but at any rates the output of the efibootmgr shows that they lack the default bootpath to bootloader’s efi binary
\EFI\endeavouros\grubx64.efi
They only have the fallback bootpath (Boot0002)
\EFI\BOOT\BOOTX64.EFI0000424f
So as already mentioned, this may not be the issue but creating the default bootpath, trying to boot from that and if the issue still persists, this will help to eliminate the Grub’s bootloader as a potential issue.
That is interesting if I would have adviced refind as bootloader no grub was needed right ?