Very useful. Thanks for sharing.

I can understand your problem because I have faced this problem. It is not the only problem that Heroku confers limited resources when you use its free tier but it also becomes very costly when you transfer your app from its freemium to a premium version. It becomes a very annoying situation for developers. To avoid this problem, I am considering Heroku alternatives from here and probably, I would like to go with Dokku with great customized plugins. By the way, DigitalOcean is also a very affordable platform itself.

I also heard a lot about Northflank and usually, developers consider it a workable option for Ruby projects. I think you should also give it a chance. You can also include OpenShift in your list because of its good reviews.