WinterCMS - CMS for developers
Earlier known as OctoberCMS, but now forked and still open source under the name WinterCMS is a CMS made for developers. The now paid OctoberCMS already got a Docker image, the forked and still open source WinterCMS hasn't, but would be great to see it available as app in Cloudron.
I tried OctobeCMS some years ago and liked it.
The important point from my memory is that it is
Not as easy to use as Ghost or Grav.
But that's not a criticism - depends on the use case of course.
I didn't know about WinterCMS but will go check it out.