Solved my own issue. Secret_Key_Base was not set appropriately, and the failure to execute bundler did not cause Capistrano to stop, it just hangs.
Other than not being able to use the Capistrano commands as listed, needed to use bundle exec, this was all straight forward. How long is it supposed to sit on bundler:install when using Capistrano to deploy? It isn't crashing, I'm not getting any error messages, but it's been over 45 minutes. If I ssh into the server from a different terminal window, I can see processes working, but I can't differentiate which process is running the bundler:install.