Following the GoRails episode on setting up Rails 7 with bootstrap, and extending it to work with Docker.
cp .env.example .env
docker-compose build
docker-compose run web bin/rails db:setup
docker-compose up
docker-compose exec bin/rails c
docker-compose run web bundle exec rspec
docker-compose run web bundle update
docker-compose up --build
Sofija Simic's article How to Install Docker Compose on Ubuntu 20.04
helped me.