When someone tells me to ‘invoke these 3 magic incantations’, I can sort of keep track of it. But here it seems like the instructions are to invoke these 300 magic incantations.
Having to jump through all these hoops (I'll note that one of the suggested gems is Devise, which provides a framework for user authentication) suggests either this is very much no longer the case or this is tacking on a lot of stuff Rails was never intended to use, which could be fun to maintain down the line.
Devise is common for user authentication (and good choice, in my opinion) but it is extremely opinionated and does not like you departing from the blessed path.
Rails tends to avoid enforcing patterns beyond the base building blocks of MVC. User authentication is out of scope. (Turbo links is strongly opinionated but also very limited and very easy to remove.)
This sounds like the second of my options i.e. gl;hf when the next major Rails release comes around.
Also - I noticed the author says "foreman is the best way to develop locally". I encourage the author to give overmind a try - it is a drop in, more featureful replacement for foreman. I love it.