Canyon have an online size calculator which takes into account height, inseam, trunk length, reach and shoulder width. Its going to be pretty close, and MTB design means that you can adjust fit with stem height, bar rise, stem length and so on. Sizing isn't as critical on a MTB in any case, and many riders tend to fall I to the trap of thinking a MTB has yo be as big as their road frame. Far better to go a size smaller and run a bit of seatpost than ago too large and end up with a five bar gate and no standover.
If Canyon and others ran free returns they'd end up payong twice for every finnicky pillock who can't make their minds up. If you want bespoke fitting, go to a MTB specific bike shop and pay the premium.