thanks to this article: https://qiita.com/me-654393/items/ac6f61f3eee66380ecd7
you should be able to use Docker CLI.
you can create your own repositry with this template.
how to setup.
bash init.sh
only this.
- rails6
- PostgreSQL
you can deploy this app to heroku without no preparation.
(of course, you should to be able to use heroku CLI)
only this.
docker-compose run web bundle install
heroku login --interactive
heroku create
git push heroku master