I have seen kids learn to ride with training wheels. Basically the training wheels are raised relative to the rear wheel and the child learns to balance the bike on the tires, with the training wheels only touching when the bike leans over. But that only teaches them how to balance the bike when riding in a straight line. Not start, turn, or stop.
One thing I think gets lost in the discussion of training wheels: people act like you have four wheels flat on the ground, with no opportunity to balance. But proper training wheels should have two or three wheels on the ground, depending on if the rider is balancing or not. In other words, the training wheels should be lifted slightly up: https://www.twowheelingtots.com/training-wheels-faq/