I think I'm almost OK with this machine after some tune here and there. And I'm using all latest drivers ON and latest windows update also.
1) Use ONLY native screen resolution and no UI scaling (are we speaking about HD version here?)
2) Turn off Clear Type
3) Never use Chrome, Firefox or Edge (give me strain in any case). I'm fine with Vivaldi and Opera browsers
4) Never use dark theme.
5) Never use plain wallpaper, use bright detailed photo instead
6) Never go to bottom 30% of brightness range — this is where PWM starts to work
7) Never use keyboard backlight. Even worse PWM.
8) Play with color profiles/video settings to reduce contrast a bit and maybe add some yellow tint (but not with windows night light, use dell utilities).
May sound like nothing big, but it went from heavy strain to usable for me this way.
And any use of HDMI cable gives me severe problems anyway.