> Although Docker meets all these requirements, I don't really like using it. I find it slow, frustrating, and overkill for my purposes.

How so? I've been using Docker for development for years now and haven't experienced this EXCEPT with some slowness I experienced with Docker Compose upon upgrading to MacOS Catalina (which turned out to be bug with PyInstaller, not Docker or Docker Compose). This is on a Mac, btw; I hear that Docker on Linux is blazing fast.

I personally would absolutely leverage Docker for the setup being described here: multiple versions with lots of environmental differences between each other. That's what Docker was made for!