Derailleur can't shift to 51-T sprocket. Deore CS-M5100 + RD-M5100
Turns out this derailleur needs a 'standard mount' derailleur pad/hanger. I have currently a direct mount.
The Canyon representative thought the SRAM hanger was for 10 speed.
To me, it is now clear that a 'SRAM' pad/hanger is the same as a Shimano 'standard mount'. So, I purchased the SRAM hanger (aka standard mount) from Canyon and it works!