Hi! I have these Ultegra 6700 shifters and a Deore 9 speed rear derailleur. They work fine, but they "lose adjustment" pretty easily. I'm thinking about upgrade into this Shimano GRX RD-RX400 (
Full rebuild - Shimano Ultegra RD-6700 road rear derailleur. How to service rear mech. - YouTube
Shimano Ultegra Fd-R8000 Frnt Derailleur | Jenson USA