Comment 25 for bug 1510731

I can confirm that this problem still exists with Kubuntu 18.04.

In my case, I'm not even setting up a separate /boot partition as I want a fully-encrypted disk.

After simply choosing "physical volume for encryption" on the only available partition, the Install Now button becomes active but clicking it does nothing. Then, clicking the Back button results in the two following errors:
* "An error occurred while creating the keyfile."
* "An error occurred while configuring encrypted volumes. The configuration has been aborted."

I have even gotten Ubiquity to crash a few times from various attempts to set up the scheme.