Not the OP, but the historical answer was POSIX (https://en.wikipedia.org/wiki/POSIX, https://dl.acm.org/doi/10.1109/2.56856).

That didn’t work perfectly, but it did work to some extent.

Just like it's done now, every distro having their own system. It containerization for people who like that.

What I have an issue with is apps making themselves dependent on systemd like KDE is doing. https://www.reddit.com/r/kde/comments/1qi9vo5/comment/o0pzvq...

Systemd does not solve the deployment problem, and will not unless it adds something like a systemd package manager.

It is interesting that Linux is far more widely used than alternatives that are not fragmented (e.g. FreeBSD) and has not standardised on one distro. Different people have different needs and preferences. People using Debian, Alpine, and NixOS are unlikely to agree on what they want.

You define the supported target and that's it. RHEL and Ubuntu LTS, kubernetes, docker/podman or flatpak are popular ones.