You might want to take a look at NixOS[0]. It is fully built around systems for services etc. and while it does allow you to, e.g., use an alternate local DNS resolver instead of systemd-resolved, it still makes it easy to build a fully immutable distro with mostly systemd components.

It does have the "downside" of not just being plug-and-play but rather BYO system.

[0]: https://nixos.org/manual/nixos/stable/#preface /