David Kimura PRO said almost 3 years ago on Deployment alternatives :
  Unfortunately, the Deployment Alternatives episode isn't looking too good right now. App Platform has a major issue with using an old heroku/ruby buildpack version. This is a problem because it will not allow for the deployment of a yarn-based Ruby on Rails application without webpacker. Essentially, you have to use webpacker and not jsbundling-rails or cssbundling-rails. I'm in talks with the Digital Ocean team to see if they can get this resolved, but as such, I will likely have to postpone this episode until they update their platform.