Comment 9 for bug 1746200

rEFInd is said 'beta quality' by its own dev http://www.rodsbooks.com/refind/

and itself rely on rEFIt which has its bugs list : https://sourceforge.net/p/refit/bugs/ but looks abandonned

http://www.rodsbooks.com/refind/todo.html

To conclude:

 intel-microcode can't be blamed at first glance. But refind have trouble to work with the microcode script. Please check: 'journalctl | grep refind > refind.txt' (after intel-microcode removal then reinstall).

Running refind over grub2 results having 2 EFI boot loaders at once !!!
http://www.rodsbooks.com/efi-bootloaders/index.html
... and that should be the main trouble source.

So test booting only with refind (purging grub2) and report back; but that one is clearly 'invalid' regarding the links above.