Always unplug the mains while working on your hardware!
Some modifications may require advanced soldering. If you have never done this before you may consider practising on something else.
I am not responsible for any damage to you or your gear.
You try the following at your own risk! If you do so....
Since the ArcherC50V3 has a MT7628AN Chipset it should be possible to add a single USB port/ or a HUB chip to it.
I analysed the mainboard, was quite easy with the MT7628AN Datasheet we can find in the internet. In good practice the engineers terminated the unused ports with 15k resistors to ground.