Where do aliens come from? They won't arrive on spaceships

If you keep backing away from assumptions about vessels, physics, etc., as you should, then you ask why would you think there is "anyone" who needs to "visit". At this point you see that ET is simply a mirror. My preferred navigators of the continuum of being are whales: floating within ancient oceans protected by a thick layer of blubber, they seem wonderfully adapted for connection via some intergalactic telemetry. The ultimate expression of their adaptation is that they don't care if they're hunted. They've got other stuff to do.