Bringing in Newton's
Every action has an equal and opposite reaction
any torque measured about a propeller (or jet core for that matter) is matched by another one.
In the piston case, it's applied by the crankshaft and resolved through the crankcase and engine mounts into the airframe.
With turbine engines, the propeller/fan receives torque from the turbine and there is no transmission of torque forces to the airframe (excepting bearing friction).
In both cases, thrust bearings carry that force to the airframe.
So yes, turboprop engines do not transmit torque to the airframe; however, slipstream effects as noted by many are quite significant and generally have a linear relationship to torque.