Does seem to support cross-architecture image building, which is a feature that's kept me on Debian's multistrap and now mmdebstrap.

I should give this a go!

The README's reference page has some good write-ups et cetera! There's a good "re-introduction" on Lennart (creator of systemd, mkosi) site, from the current maintainer.

https://github.com/systemd/mkosi?tab=readme-ov-file#referenc... https://0pointer.net/blog/a-re-introduction-to-mkosi-a-tool-...