I asked for my brother to bring me his Dell VA panel SE2216H releases in 2015 and it was fine. Asked my friend to bring his LG Ultrawide 29WL500 releases in 2019 with IPS panel and it was ok. A little bit grainy the reflection but not near the P2423D.
I returned the P2423D and bought a LG Ultrawide 29UM69G that was released in 2019. I searched a lot of videos to see at least the reflection characteristics and found that 29WK600 from 2018 was more like the Dell that I returned and the one that I bought was like my previous Dell.
And that is it. The antiglare screen seems almost the same as my Dell and the image quality and characteristics not so distant. I've been using and no difficult on focusing, no strain, no eye pain, no headache and stuffs like that.
Something very weird has been happening since 2018. I don't believe that is only the antiglare screen but it plays a role. I solved my problem for now with 2017 stuff but next time I doubt that I will have another chance. I would like to figure out what are the problems and how can I discover before I bought.