I wrote a blog post about using nspawn from an Arch Linux host. The Arch Wiki shows more information about how to get a Debian base if you want that instead. Link to the wiki is at the bottom of the blog post along with more references.

https://adamgradzki.com/lightweight-development-sandboxes-wi...

Portable services are another option.

And podman systemd quadlets yet another

https://docs.podman.io/en/latest/markdown/podman-systemd.uni...

Wow systemd can do more than I thought to imagine it could

Technically that's part of podman, not systemd. But it's the same architecture that was used to support sysvinit scripts.

(In fact, nothing prevents anyone from extracting and repackaging the sysvinit generator, now that I think of it).