Current lore seems to be if it's a ship with a toilet, Artificial Gravity has you covered - or should I say not covered in doo-doo, and anything without is intended to be a short-haul craft, like the single seat fighters etc. No toilet, the ship probably doesn't have the range to need one.
I also recall an official Lore story where a guy was transporting a ship from the Yards to the customer and to retain that new ship smell the polit stayed in their flight suit hermetically sealed away from the ships own atmosphere, and took some metabolism altering pills to ensure they didn't need to go to the lavatory for the duration of the flight which was several days.
Can't imagine what happened when they finally got to a bog, but I can't imaging it was not as dense as a neutron star.