@krichtof My blog1 and the demo site2 for my first open-source theme3 run Ghost on Heroku with the stock frontend. Because Heroku doesn’t play well with Ghost 2.0 — among other reasons* — these are running Ghost LTS.
For the demo4 of my most popular premium theme5 I’m running Ghost 2.x on AWS (using Dokku). It’s not as simple as DO or Ghost PRO, but I have other apps on the same machine, so it’s cheaper, and once you have it figured out it’s fairly low-maintenance.
The demo sites for my open-source Ghost starter theme6 and my most recent premium Ghost theme7, which I don’t need to update as frequently as a blog, are static sites generated from a local Ghost 2.x install using the Buster python script8, hosted on GitHub pages. Buster is technically unmaintained, but still works, and saves on hosting $$$ for sites that you aren’t posting to every day.
tl;dr — 3 of the 5 of the Ghost blogs I maintain are using the stock Ghost frontend, and other 2 are static sites generated with Buster. Running Ghost normally is more convenient, especially for frequently updated sites, but hosting Buster-generated static sites is free, and static sites have a smaller attack surface.