Oh you do: this work completely differently from sudo, there is no suid binary involved, instead it does IPC to the systemd pid 1 and asks it to spawn you process, attached to your current terminal. So if you don't have systeme as pid 1, it'll have noone to talk to.

Whether you like that or not is for you to decide.

IPC will likely be over d-bus. The new process will fork off a systemd which is almost always pid 1, but it might not have to be.

are there any non-systemd DBus options anymore? I had a hard time a year ago setting up Gentoo because there were no maintained options at that time.

There are. Gentoo has actually always used the FreeDesktop reference implementation instead of sd-bus (the systemd implementation).

FreeDesktop also maintains a list of implementations (also including bindings so you have to read to find which ones are full impls vs libdbus bindings).

https://www.freedesktop.org/wiki/Software/DBusBindings/