Comment 3 for bug 1509877

Although perhaps not a "duplicate" of Bug #1523194 that I reported, the two bugs at least seems related.

Have you tried installing only into boot (/boot) and root (/), and then moving home to a separate auto-mountable encrypted partition after installation has completed? (To get this to work, you'll also need to skip creating a swap partition during installation, and then create a swap partition, or a swap file, once installation has completed.)

For more details, see https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1523194