BGR - RGB Pixel layout problem. How to fix wrong subpixel optimization in "LCD font smoothing"
Solution 1:
You aren't going to like it but turn it upside down.. Then you will get RGB
Solution 2:
The way to "fix wrong subpixel layout setting on Mac OS" is using System Preferences, Display, Rotation 180 degrees (from Standard). This makes an external LED display switch from BGR to RGB pixel orientation.
However you also complain your fonts look terrible. Under System Preferences, General, uncheck Use LCD font smoothing when available. Now ALL fonts will look identical in EVERY orientation. If you do not believe me, then make your whole monitor display white and rotate 90, 180, 270. Do the colors change? No. Because if you disable font smoothing then every font is made from WHOLE pixels.
So without font smoothing if your fonts still look terrible, then your problem has to do with something else and NOT BGR or RGB pixel orientation.