Shimano Ultegra R8000 short cage rear derailleur has a max drivetrain capacity of 35t. A medium cage is 39t
54 - 36 = 18
28 - 11 = 17
18 + 17 = 35
Technically...that could still work, if you found a 54t crank that works with a 2x drivetrain. Otherwise you can always use a medium cage.