Comment 11 for bug 1847944

>I wonder if disks is preseeded or not.

Yes, a script detects the disk to install to, but it essentially ended up as:
d-i partman-auto/disk string /dev/sda

>It would be nice if one could boot the recovery, upgrade ubiquity, from that ppa, and see if the autoinstall stuff still works correctly.

This will take a little effort to get slipstreamed into the test environment. I'll let you know.

>And I assume that one has called:
>echo ubiquity partman/filter_mounted boolean false | sudo debconf-set-selections
> or preseeded that key in any other supported way.

Yes:
d-i partman/filter_mounted boolean false

has been preseeded.