FWIW, I moved from Jekyll/Netlify CMS earlier this year.
I found an old Jekyll -> ghost importer (painful: had to install Ghost 1, import there, upgrade ghost, export, and then import into my ghost.org blog) which got me “most” of the way there … but, it doesn’t do anything with the actual post content, so my really old blog posts are in ghost but are pretty ugly with liquid tags.
As someone who moved from Jekyll, I am still loving ghost. I have been horrifyingly busy at work the past month so I haven’t blogged much, but I’ve still dashed off a few things for fun. I’ve managed to integrate a bibtex system, and export custom .rss feeds for my micro.blog (a few of the things I liked about my old jekyll setup).
(fyi, my blog is at blairmacintyre.me … the front page needs a bit of work, but I’m happy with the various blog pages)