Hi,
A humming motor usually indicates either a faulty motor start winding or perhaps the [https://www.buyspares.com/lg/tumble-dryer/catalogue.pl?shop=lg&path=111339&model_ref=11803640&refine=capacitor|motor capacitor] (supplier example only) may be faulty. It seems that the motor is trying to start on the run winding only and this doesn’t produce enough magnetism to start the motor rotating, therefore the hum.
The capacitor is there to increase the torque of the motor on startup if it is wired as a start capacitor or to improve the efficiency of the motor if it is wired as a run capacitor. I don’t know which it is in your dryer.
The current flowing through both windings ensure that there is sufficient magnetism produced to overcome the inertia of the motor from the at-rest position and once the motor is up to speed an internal centrifugal switch operates and disconnects the start winding from the circuit, allowing the motor to run on the run winding only.
Here’s a link to the section of the [https://www.manualslib.com/manual/850380/Lg-Rc9011-Series.html?page=15&term=motor&selected=3#manual|service manual] that shows the resistance values of the motor windings and also the capacitor, which may help.