Another trick to try is this ziptie method.
Yes I know that's a motorcycle tire but I've done it with my motorcycle and was shocked how easy it was with some lube on the beads. Never done it with a bike tire but an MC tire is a real brute to do even with big steel tire irons which is how I used to mount them so imagine a bike tire would be easier. The goal is to tie the tire so the beads are together. Not the most convenient thing to do out on the road but works well when mounting a new stubborn tire without drama.