GNOME and KDE images will be built with systemd by default. while using systemd will be optional, polyfills - a somewhat messy way of providing systemd features with other init systems - are the only way to support GNOME and KDE and will eventually become unmaintained by PostmarketOS.

not too sure how systemd was implemented, but it looks like systemd is just built with musl libc as systemd is mostly compatible with it.