amd64, arm64, arm64-graviton2, ppc64le (IBM Power), s390x (IBM Z) docker
Supported Architectures
<https://help.ubuntu.com/lts/installation-guide/armhf/ch02s01.html>
Building on Multiple CPU Architectures
https://docs.travis-ci.com/user/multi-cpu-architectures/
The Ubuntu Linux Build Environments
https://docs.travis-ci.com/user/reference/linux/