I was asking, because I had a similar discussion with an Asus RT-AX53U, where wget was recommended and scp "could" work. With the RT-AX53U it is not se easy as with the WSM20, but hopefully not difficult.
Maybe you can say something in MT7915 vs MT7905 vs MT7975: ZyXEL WSM20 vs. Asus RT-AX53U Till now, no answer.