CoCalc cocalc.com has all the tools you need to author with MathBook XML. You will need an upgrade from a subscription to allow Internet connectivity, but at a minimum a colleague with a paid plan can spare you one, they are plentiful and meant to be shared.
Text editor: reasonably good, partially XML syntax-aware.
git: installed (so clone PreTeXt).
LaTeX: installed with many additional packages.
Python: installed, necessary for mbx script.
PDF viewer: handed off to your browser.
HTML viewer: convert to the “raw” URL and you can preview.
HTML server: nope. Zip up output and host elsewhere.