Current(8.08.17) Neon installation ISOs(both the userlts and user editions) fail to install GRUB on UEFI systems. This is due to the lack of a /usr/lib/grub/x86_64-efi folder containing the appropriate configuration. I believe this is because someone tried to get rid on an earlier bug(can't find a link now, sorry), thanks to which grub was misconfigured and installed partially to /efi/ubuntu and partially to /efi/neon. Now it doesn't install at all. The installation from Calmares fails to install with a "failed to install to /target/" message. I tracked this bug by trying to do a chroot install, as per https://help.ubuntu.com/community/Grub2/Installing#via_ChRoot which revealed a message saying "grub-install: error: /usr/lib/grub/x86_64-efi/modinfo.sh doesn't exist". Closer examination revealed that the whole folder was missing.
Possible duplicate of https://bugs.kde.org/show_bug.cgi?id=366463 as I installed without an Internet connection
Yep. No internet connection does that. *** This bug has been marked as a duplicate of bug 366463 ***