Wey Slops - Overboard
Yes, there were aircraft that discharged toilet waste overboard - Back in 1950's at KIDL I regularly worked a DC-4 belonging to a large oil company. It, along with two DC-6 aircraft regularly flew from the Mid-East to New York. - the lavs had a sign on the door, "DO NOT USE OVER INHABITED LAND".
When you looked at the bottom of the bowl, you saw a stainless steel pipe continuing on down to daylight -
Outside was a stubby open-ended extension of said tube.
No valves, never clogged.
Their DC-6 aircraft had standard toilets for the type.
I admit its the only aircraft like that I ever saw - there was a precedent though. In America, in the good old days, the passenger trains had toilets with signs on the door, "DO NOT USE IN STATIONS".