how to asking libdbus for no D-Bus: run with DBUS_SESSION_BUS_ADDRESS="" in environment.
dbus-launch(1) man page says if DBUS_SESSION_BUS_ADDRESS is not set, it means "autolaunch:". So try to convience dbus that I really want to *not* run it.
(note: it is still in testing... maybe nowdays it is really a mandatory componment. let's see what doesn't work)
second try with DBUS_SESSION_BUS_ADDRESS="no:" as launching keepassxc still triggered dbus-daemon launch.
/me should go reading libdbus code source