https://jj-for-everyone.github.io is the most approachable jj tutorial I've seen. I wouldn't say it focuses on workflows, but it does take a "learn by doing" approach a bit more than the "data model first" approach it sounds like you might prefer.

It's still a young tool, it's not surprising that tutorials are a bit lacking (honestly there are surprisingly many for its age). Maybe be the change you want to see in the world and make one? (Which would be an... interesting... way to learn the tool for sure).