I tried your procedure on a relatively modern PC I use for experimentation. After I made one addition and one correction it worked.
When I did the above step I got:
sputnik3:~ # update-bootloader --install --config
target = x86_64-efi, update default location = 1
+ /usr/sbin/shim-install --config-file=/boot/grub2/grub.cfg
/usr/sbin/shim-install: line 251: /usr/sbin/grub2-probe: No such file or directory
efi_distro_dir=opensuse
efi_order=0003,0001,0002,0004,0005,0006
efi_entry.num=0003
efi_entry.file=EFI/OPENSUSE/SHIM.EFI
efi_entry.name=openSUSE Boot Manager
I needed to install grub2-efi.
I also got another error:
sudo rm -r /boot/loader/entries/*
rm: cannot remove '/boot/loader/entries': No such file or directory
I think that’s just a typo.
I think the correct steps are:
sudo editor /etc/sysconfig/bootloader # I used vi as my editor
sudo zypper install grub2-x86_64-efi
sudo update-bootloader --install --config
sudo rm -r /boot/efi/loader/entries
sudo grub2-install --target=x86_64-efi --bootloader-id=opensuse --efi-directory=/boot/efi
sudo reboot
On booting, I now see the old grub2-efi menu.
I probably should have done a sudo efibootmgr -v to check for opensuse entry being set to \EFI\OPENSUSE\GRUBX64\EFI as well, but I forgot that until after rebooting.
In the long term it might still be a good idea to enlarge boot-efi to 4GB (on this particular machine, my current boot-efi is above 1GB due to me untidily keeping a few kernels around).