Having looked more closely this bug was a result of user error; I did in fact repartition the installation device and had a separate partition for /boot/ which was also LUKS/dm_crypt. I had forgotten I needed to edit the /target/etc/default/grub whilst ubiquity was installing GRUB, and had to do it manually after ubiquity had completed.
This bug is about ubiquity actually *crashing* due to the package install failure rather than doing a clean error report and user- controlled quit. For that reason I'm re-titling the bug so as not to distract from this bug reason with the mention of the GRUB_ENABLE_CRYPTODISK. ** Summary changed: - 16.04 installer failed during grub-install with error: attempt to install to encrypted disk without cryptodisk enabled. Set `GRUB_ENABLE_CRYPTODISK=1' in file `/etc/default/grub' + 16.04 ubiquity crashed due to package-install failure of grub2 during grub-install step -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1572754 Title: 16.04 ubiquity crashed due to package-install failure of grub2 during grub-install step To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1572754/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
