Bonded MOCA adapters? I used one to repurpose a satellite line that went to an awkward location. Needs power, and while the throughput and reliability was definitely better than wifi, the latency felt pretty high.

POE seems to use either the data or spare pairs for power depending on which mode it uses (A or B), while POE++ uses all four pairs.

While conceptually it sounds like if you can guarantee only mode A usage you could put dual POE connections on a single cable, I don’t seem to see any adapters that do this.