Not specifically 21.9 related but a decent tutorial for the 29" LG monitor and how to remove the matte coating (should also apply to all the other 21.9 screens):
https://hddcaddy.eu/remove-anti-glare-coating-from-lg-29um68-monitor/
Might try it myself sometime this year considering my monitor's warranty ended a good couple of years ago now.
https://hddcaddy.eu/remove-anti-glare-coating-from-lg-29um68-monitor/
Might try it myself sometime this year considering my monitor's warranty ended a good couple of years ago now.