Hanging Cables Along the Corners of Walls
Command strips &quot;cord bundlers&quot; and a nice hunk of decoy fake Ivy or other imitation vining plant (unless there's enough light and willingness to care for to use a real plant - unlikely.)
Alternatively, fairy lights, etc.
Basically, it will be in plain sight any way you slice it, so might as well just make it disappear by having something more noticeable that makes it non-obvious (the decoy need not stop where the ethernet wire does, either, which can help.)