I have created a Docker container that can be used in CI systems to build Android packages out of Ionic apps. It is specifically tailored for Gitlab CI, but should work on other CI systems that support Docker workers.
The image also contains the tools necessary to send the file to beta testers (via email) or upload it somewhere (via sftp, scp, rsync).
Please let me know what you think and feel free to create pull requests if you miss something.
Tobias from Healthcast