Follow the guide again, arch-chroot then grub-install, or maybe you can try to use rEFInd as suggested by others.
Other option would be to arch-chroot, downgrade grub and ignorepkg in pacman.conf
Lastly, you could follow Dalto’s guide and convert to systemd-boot
https://forum.endeavouros.com/t/tutorial-convert-to-systemd-boot/13290