What Intruder has said in the second sentence is absolutely correct for a jet aircraft, but certainly not for a propeller aircraft.
So, at a given weight, lift is constant in level flight, and thrust required is directly proportional to drag.
AFAIK, the L/D max / max endurance equation works for any powered aircraft. I don't know how max endurance at a constant altitude can be at a lower airspeed.
OTOH, I am also aware of the minimum sink speed for a glider, which is at the maximum lift speed ( just above stall), and lower than the max endurance speed for a powered aircraft.
Maybe there are some technical nuances to the definintions used in the various publications...