This is definitely strange, but the EFI system partition will have to be mounted to install grub to it, maybe the disk got mounted as read only, could you try explicitly mounting it as rw with this command
sudo mount /dev/nvme0n1p1 /boot/efi -o rw
and then see if you can make a file as root by doing
sudo touch /boot/efi/test
if it doesnt fail on a permissions error, try installing grub again with --removable
incase this error has something to do with it trying to tell the firmware what disk to look in like this
sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --removable
hopefully this will run without error and install grub, and if it does id run it again without the removable flag
Oh its no worries, it sounds like you just need to regenerate the grub config, you can do this by running
or if your distro has it, you can just run
then grub should see the config on boot and put you in the normal graphical menu