Thanks! I was actually able to find your older forum comment and with minor adaptation I could restore grub:
mount /dev/nvme0n1p8 /mnt
mount --bind /dev /mnt/dev
mount --bind /sys /mnt/sys
mount --bind /proc /mnt/proc
chroot /mnt
mount -a
grub2-install --target=x86_64-efi --efi-directory=/boot/efi --removable
Those arguments to grub2-install seem to be crucial for it to work, but I’m not sure which of the three solved it. I followed this StackOverflow solution.