Rails 7 Guide Instructions... incomplete?

I was running into some problems with my own understanding. So I wanted to take a full-pass at rails 7 again.

So I’m at the ‘Installing rails’ step #3.1.4 at the beginning of rails guides and the verbatim instructions already are not working.

gem install rails ~ stuff happens → great rails --version → NOPE

I can create a local Gemfile…
bundle init
bundle add rails
rails --version

Is not what I was looking to do because I ran into bootstrap problems with the nested application. ( or at least that’s what the relevant stack overflow said? )

If Gemfile IS the way we’re supposed to do this, then why isn’t that in the guides? If nested bundle Gemfile is NOT how I’m supposed to do this, what horrible thing am I doing wrong? (Definitely user error, same issues on ubuntu 20.04, and up-to-date archlinux)

Postgres 14.0
Ruby 3.1.1
Nodejs 17.8.1
Yarn 1.22.18

I’m curious about “stuff happens”: what exactly happened? What did the gem install rails output? I suspect that it printed some important error message.