This question begins the same as this question:
Is weapon reach measured from the edge of the mount's space or the rider's?
However Rubiksmoose's answer (the currently accepted answer) seems to contradict JA Streich's answer and Ilya's answer, the other two highly-voted answers. Plus, the highly-voted ones seem to suggest that it is kind of up to the player, or at least in favour of the player.
My question is then about how this all applies to a character wielding a lance while riding a large creature.
If the mount is right up against the enemy, can the character on the mount attack with the lance without disadvantage, because they are in fact not within 5 feet?