The Linux base image is constructed using Ubuntu 16.04 as a "common base".

However, the manylinux image might be a better baseline. This is the baseline image that is used for Python wheels on Linux, so it should be a better starting point for long-term compatibility.

The Docker image is available as: quay.io/pypa/manylinux2010_x86_64.

Briefcase moving to a Docker-based build chain for Linux makes the transition easier, as we can run the build in a manylinux container. However, part of the investigation will be whether it's possible to natively host Linux builds based on manylinux support package (i.e., not use docker for the image build, but use a manylinux support package). My understanding is that this should work, but we need to confirm.