Looking at grub.cfg will reveal
initrd /boot/intel-ucode.img
where it should say
initrd /boot/intel-ucode.img /boot//initramfs-linux.img
Of course the fallback image boots fine.
One workaround is to edit grub.cfg manually.
A very dirty workaround is to pull the os-prober and grub packages from M---- and install locally since those are already fixed. If you do that you'll need to edit the pacman conf file ignore updates for those packages. The patch for os-prober (specifically, 30_os-prober script) seems to be https://bugzilla.opensuse.org/attachment.cgi?id=780376 but I haven't looked to see what changed in grub. (If I have time this weekend I'll look into it more).
]]>