Rails Tutorial is probably the single most influential training course among the Rails community -- at least anecdotally.
I have worked with dozens of Rails devs over the years and in my estimation at least 80% have done the Rails Tutorial. In my opinion, it's the single best resource for learning Rails in a way consistent with real-world best practices.
Not free, but if you don't mind paying the cost of 2x pizzas you can get life time access to a 10 hour self paced video course that will teach you how to build a large real world application with Flask and Docker.
Instead of building a watered down application, it concentrates on building a production ready application. Instead of a Twitter clone, we build up a payment processing application that protects a game behind multiple tiers of pricing plans.
Some students are building their next start-up based on the code examples used in the course. One student even landed a $5,000+ contract a few weeks after taking the course.
Details (along with a demo video showing exactly what we'll build) can be found here:
I'm not sure if you're complementing or insulting the technology choices, but thanks... now I'm in the mood for bread sticks.
Tons of students loved the Docker content. It is definitely secondary to learning Flask but you learn enough to get comfortable using Docker in development. It's what we use to set up a development environment.