It's a bit heavy handed, but the VSCode "Live Server" plugin is the closest I've come. If I set code as the default file association for `.html`, then it's just one extra click to get it open in a browser with a local server.

This isn't going to work for everyone, but if you're dealing with non-tech-savvy but mostly-able-to-use-a-computer users, it can, and it being graphical seems to be less of a hill than if I tell people to run `python -m http.server` in the terminal (because, "what is a terminal"...)