I know this post is a bit old, just wanted to add that I do have backlash compensation up and running.
The latest firmware has backlash compensation with M425 enabled, the only caveat is it’s not able to be stored in firmware. That’s no big deal though as I created a custom “Home” macro in Luban that contains the M425 command, as well as adding it to my slicers so all gcode files contain the appropriate command before it homes.
The syntax is here: https://marlinfw.org/docs/gcode/M425.html
I measured Z backlash using the calibration card and sending + and - Z movements in custom increments of 0.01mm. I measured X and Y using the following model: https://www.thingiverse.com/thing:2040624
I found each axis on my machine needs 0.03mm of backlash compensation (very good, in my opinion!) so my files contain the following:
M425 F1 S0 X0.03 Y0.03 Z0.03
Your mileage may very! Good luck!