I don't know if a GRX 1x crank will fit a 34 or 32 ring.
You could look at SRAM.
I've also seen MTB 1x Di2 setups using an XT or XTR rear derailleur and TRP Hylex Di2 kit.
https://www.google.com/search?client...=trp+hylex+di2
With the exception of a SRAM solution, all of these would have to be pieced together and expensive.
-Tim-