If Canonical and RedHat weren’t backing different horses (Snap vs Flatpak), I could see the app containerization system coming under systemD as well fairly soon. The Cosmic DE project uses functionality from systemD to overlay changes onto the system that are reversible, so that alpha versions of Cosmic can be tested without permanently changing the base system. Imagine apps shipping on whatever container runtime, and dynamically overlaying system-level changes as needed for things that tap into the host system via systemd-sysext.