Installation - partition manager is breaking

[Kenneth Wrede]

Daily kubuntu, clean install in virtualbox

I wanted to try if it is possible to have an encrypted boot partition too, like openSuSE.

I opted for manual configuration of the partitions and created a new partition table. First i created a small (1G) partition and chosed "encrypted storage" (or whatever it was called) instead of a file system. I closed the dialog window.

Then I did the same thing with the intended root partition. It crashed when i closed that dialog.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.2
ProcVersionSignature: Ubuntu 5.3.0-18.19-generic 5.3.1
Uname: Linux 5.3.0-18-generic x86_64
ApportVersion: 2.20.11-0ubuntu9
Architecture: amd64
CasperVersion: 1.432
CurrentDesktop: KDE
Date: Sat Dec 7 11:58:36 2019
InstallCmdLine: file=/cdrom/preseed/kubuntu.seed maybe-ubiquity initrd=/casper/initrd quiet splash --- maybe-ubiquity
LiveMediaBuild: Kubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20191202)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[oldfred (oldfred)]

Similar issue with Ubiquity 20.04.3 as of Dec 7, 2019.
Installing to sdb, asked it to unmount sda partitions, but it said it could not unmount sda5 where isodevice is mounted.
Selected to not use ESP on sda, but use ESP on sdb, unselected swap on sda & swap on sdb. Install to sdb12, format and use as ext4 & use as /.

Lots of warnings & error messages
GtkBox does not have a child property
XDG_RUNTIME_DIR (/run/user/999) is not owned by us (uid 0)
Gtk-CRITICAL gtk_widget_set .. failed
/usr/lib/ubiquity/plugins/ubi-usersetup.py:372: Warning: Source ID 12889 was not found when attempting to remove it
  GLib.source_remove(self.hostname_timeout_id)
Gdk-Message: 13:41:25.443: ubiquity: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.

[oldfred (oldfred)]

For me I forced the unmount of /dev/sda5 which is where /isodevice mounted.
sudo umount -lrf /isodevice

Similar issue:
https://askubuntu.com/questions/1157619/install-cannot-modify-hard-disk