I'm not aware of any production version of Chordite (that this design is based on) as of now; but in the wider family of chorded keyboards, the one with a production version that I'm aware of is the Twiddler.
https://wearables.cc.gatech.edu/projects/twidor/screens.html
For learning, I personally just try to slowly code simple hobby things in vim, with the cheatsheet in the other hand... I tried to make the layout relatively intuitive wherever I could. I also patiently went through all the possible combinations of presses, and tried to group them into categories of easy<->medium<->hard<->impossible, then tried to put esp. the more frequently used keys on the easier combinations/chords.