It is 11-speed only, but compatible with any of Shimano’s other 11-speed road shifters ... Our Allied Alfa All-Road test bikes had a compact 50/34t Dura-Ace crankset paired with an 11-32t rear ...

The GRX RX400 rear mech does not work at all with 10-speed Ultegra because it needs more cable pulled per click. Not a lot more (like SRAM and Shimano MTB 10-speed) but just a little – like Campag.

Shimano 105 Di2 Hydraulic Disc Brake Dual Control Levers (2×12-speed) – Left (front derailleur/brake) and Right (rear derailleur/brake ... but that doesn’t include the hose plus brake fluid On my ...