The online documentation reflect the current head of the main branch, which will (once Docker is fixed) correspond to the rmg or rmg:latest docker image. There is no (obvious) way to get documentation for the 3.2.0 release, which is what people are instructed to install. Given that the command to even run it (python vs python-jl) is different, this is a problem.

Minimally we should have a PDF somewhere for releases.
The installation instructions should link to it clearly and distinguish which version is being installed and where to find the docs (PR #2806 is a start)

One option would be to create full HTML documentation builds in subfolders for each release, and using a version switcher in sphinx template like https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/version-dropdown.html
(like Cantera now does).

Another option could be to build a LaTeX/PDF build of the documentation for each release and add as a binary asset to the releases on github. Then there would at least be a (presumably fairly stable) URL for each.