Complicated md/lvm/dm-crypt setup. Grub failed to install due to lack of bios_grub FAT32 partition. Space was reserved but didn't know it was required for non-EFI system using GPT drive label. Used gparted to format and set required flag on partition then chrooted into /target and grub-install to fix it. Returned to grub failure dialog. OK disabled for everything until a different partition selected. Then chose to continue without bootloader since I had manually installed it from chroot. Error dialog displayed and apport submitted it.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.2
ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13
Uname: Linux 4.4.0-31-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CasperVersion: 1.376
Date: Thu Jan 19 02:07:48 2017
InstallCmdLine: BOOT_IMAGE=/isomnt/xubuntu-16.04.1-desktop-amd64/casper/vmlinuz.efi initrd=/isomnt/xubuntu-16.04.1-desktop-amd64/casper/initrd.lz boot=casper netboot=nfs nfsroot=192.168.11.5:/srv/tftp/isomnt/xubuntu-16.04.1-desktop-amd64 nomodeset xforcevesa --
LiveMediaBuild: Xubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
ProcEnviron:
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)
Note that to install with my specific drive configuration most all partitioning, raiding, encrypting, and formatting have to be performed before starting the installer. The installer partition configuration dialog is only used to set mountpoints and choose the target partition for grub.