Have you tried loose bottoms with no underwear? And then build up to underwear underneath.
We are at the same point; naked with potty or toilet..fab. Pants on, she thinks its a nappy Going to preserve but just to say, we're in the same boat x
I’m so sorry I have no advice but I am in the exact same position as you with the underwear! It’s so hard, I’m hoping one day it’ll just click & in the mean time I just have to keep changing her underwear x