In case this helps anyone, I’ve had issues setting up the rails source code. Here were the solutions:
In Gemfile, change
gem 'rails'
to
gem 'rails', "~> 6.1.3.1"
Then run
$ bundle update rails
Then change
gem "activerecord-postgres_enum"
to
gem "activerecord-pg_enum"
and run
$ bin/setup
Then, I needed to jump into the three view files: box.html.erb, intro.html.erb and page.html.erb and remove a LOT of these. 38 in total:
<%
which seem to appear before and after most elements.
Finally, I needed to delete the .browserslistrc file as it was conflicting.
THEN, I was able to run
rails server
and see the app.
I hope this helps someone and fingers crossed these changes can be made to the files to make it a bit easier for the next person.