Trouble setting up the KDE PIM Docker image

[Glen Ditchfield]

I'm trying to set up a KDE PIM Docker image from scratch again
(https://community.kde.org/KDE_PIM/Docker), but I ran into an error.
When I `cd` into the kdepim-docker directory and run `./build.sh`,
it fetches many packages, begins unpacking, and then stops with
these messages:

Preparing to unpack .../202-kuserfeedback-bin_1.0.0+p18.04+git20200823.0037-0_amd64.deb ...
Unpacking kuserfeedback-bin (1.0.0+p18.04+git20200823.0037-0) over (0.0+p18.04+git20191003.1159-0) ...
Errors were encountered while processing:
 /tmp/apt-dpkg-install-xnTKYE/130-plasma-workspace_4%3a5.19.4+p18.04+git20200812.0222-0_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
The command '/bin/sh -c apt-get update && apt-get dist-upgrade -y' returned a non-zero code: 100

Does anyone have some suggestions?