You need to expand your horizons. Can’t depend on one platform nowadays.
A Just follow my advice in my first post: upload with max quality and full size. Toggle the high quality button or whatever you need to do on FB. Why do this? Because FB’s settings and compression change all the time! So if you use one method, it likely won’t work later on.
B Another strategy is to reduce your image to the lowest memory footprint possible; then FB won’t want to reduce it any further.
C1 has an idea of what FB does to the image (via connections and mainly $$$), so it applies the correct compression and optimization in advance. If it matches or is close to FB’s, then FB doesn’t distort it as much.