Your installation medium contains a mix of trysty and wily. You need to format a USB stick before reusing it to install a different distro/release.
** Changed in: grub-installer (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1518427 Title: Trying to install Ubuntu 14.04 dual bood wth Windows 10 and grub cannot be installed on an efi partition To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1518427/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs