Ok. How about this, take the Asus downstairs and connect it's wan directly to Lan port on ISP router, thus circumventing the power line, then attach a GB switch upstairs via the power line plugged in to Asus, this will give me Lan ports upstair ?Leave your ISP router as is, put your RT-AC86U in DMZ on the ISP router, connect all your devices to RT-AC86U.
https://www.snbforums.com/threads/new-rt-ac86u-starting-from-scratch.60088/#post-525927