That is another catastrophe waiting to happen. The folks there are trying to steer towards systemd-boot. With F30, they are making grub all in $esp. Its grub.cfg is placed in $esp, not /boot. If you do configfile, try to see if there is a grub.cfg in its $esp, there may be 2 grub.cfg. One in /boot and another one in /boot/efi. See if the configfile to the one in /boot/efi works. Oh remember to 'insmod fat'.
I got confused.
The multiboot core.img way was fine. It was the configfile method that didn't work at first because F30 had made changes to grub that were adverse to people on MBR boot. It didn't generate grub.cfg after I upgraded from F29 to F30 with its resultant new kernels. So trying to boot into F30 for the first time using the configfile way gave me an error message.
With the multiboot way, I was able to boot into the last kernel I was using in F29, but then I discovered the next dubious direction taken by F30 when I tried to update grub - F30 disabled by default the ability to generate grub with the grub2-mkconfig command.
Thankfully a forum member here showed me how to enable the mkconfig command again.
So there is no grub.cfg in /boot/efi. It's still in the /boot/grub2 folder. The main issue now is whether, after a kernel upgrade, F30's grub will auto generate grub.cfg like it used to, or will I have to manually use the mkconfig command after every kernel update.
IIRC, manual generation was needed the first time I updated after enabling the workaround. I seem to recall that upon first reboot after that said update, the first kernel in the grub menu was not the latest one. But I couldn't be certain and I just did a mkconfig anyway without confirming the issue.
Today, I tried to confirm this once and for all but there were no kernel updates. I'll post when I know for sure.