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Thanks for this, I'm not sure about the sharpness (coming from a Retina display the 13" MBA before 2018 seems extremely dated!) but the contrast is finally sorted. I noticed the washed out screen as soon as I turned it on!
 
Will it work with LG external display?
Generally no. That calibration profile is intended specifically for internal display characteristics.

Your external display should have its own contrast adjustments.
 
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