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Loads on that internet around this, here’s a randomly selected quote about Shimano 11 speed MTB compatibility:
‘Rear shift ratio is around 1.1. Compatible with Shimano MTB 11 speed shifters. Shimano calls this system Dyna-Sys, same as 10 speed MTB, but they’re not compatible!’
Jtek classify your case as ‘Shiftmate X’ which isn’t a product they sell, it’s just a way to say it can’t be done : (
Is a 10s M786 XT RD going to work with an 11 or 12s Shimano shifter? I’m guessing no.