Should have said, but this was on a Dell XPS 15 9550, with Windows 10 already pre-installed.
Workaround for me was to disable SecureBoot manually in the BIOS before booting the 16.04 installer. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1567445 Title: ubi-prepare failed with exit code 255 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1567445/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs