Standard (i.e. short cage )Ultegra RD works with 11-28.
A long cage Shimano road RD will work with an 11-32 (Although Shimano won't vouch for that, it does work, but you may have to play with the B screw a bit.)
As others have mentioned, you can put a Shimano MTB derailleur on as well. Just make sure it's not a " low normal" derailleur.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.