The typical way for Python docs is to host on read the docs and the code is for a docs site built in Sphinx, which uses Python.
See this page of the help.
https://docs.readthedocs.io/en/stable/versions.html
Note also the v:latest bit in the bottom left of the page to switch versions.
Or this R package which has a great variety of stable, latest and v1.x versions to choose from.
https://xgboost.readthedocs.io/en/latest/R-package/index.html#
Sphinx supports Markdown and reStructuredText so you can write your docs like before and you won’t have to worry about a theme. You’ll just have to leave Jekyll behind.
Or maybe versioned documentation is not so important - someone could always serve up an older tag docs site of yours if they really need it.
You can also try GitBook, which gives you one free public site to host and you can optionally control the site using a repo, so that is close to a Jekyll experience.