As of right now, I have set it up like this:
* In the already exisiting `./templates/privacy.html`, i cut the legal part, and put it in `./legal.html` (located in the repository root like `./config.ini` and `./logging.ini` and so on).
* This `./legal.html` is gitignored, so that it doesn't sync. Instead there's a `./legal.html.example` to give an idea what has to be put into it.
* the backend reads this `./legal.html` and passes it to Jinja2 when rendering the template of `./templates/privacy.html`.
* Jinja2 fills in the passed string, and unescapes it.
* Problem left: how do I get Jinja2 to also render the variables inside `./legal.html`?

This is how you wanted it to be set up, right? Not part of the git repo, but dynamically filled in from another gitignored file?