[Redmi K20 Pro / Xiaomi Mi 9T Pro Themes, Apps, and] Espmic86:
1) install xiaomi.eu stable 11.0.5.0 / Evolution X 3.5

2) Install magisk through TWRP, reboot to system.

3) install all your favourite modules in magisk, but primary install "disable HW overlays" 2.1 module, thanks to LEN, there is a telegram group where to download it: http://www.t.me/LenScreenOC [MENTION=901293]t.m[/MENTION]e/LenScreenOC

NOW TAKE A BACKUP THROUGH TWRP of BOOT and DTBO partitions, cause if something goes wrong from now on with kernel and dtbo you can reinstall backed up partitions.

3) Install through twrp the Immensity 8.2 kernel, thread on xda.

4) Install still through twrp the the 75hz dtbo for evolution x 3.5 found on caballero's drive https://drive.google.com/folderview?id=10NSW_b4Jqh2Sxgy-bKe0j9Tn1i1H5aWx , somehow this is the only working dtbo, even if we are talking of xiaomi,eu rom 11.0.5 android Q, this only works... if it does not work for you try LEN dtbo's version 12.18 (latest, a zip file with all dtbo's for all desired refresh rate) on his telegrram group (the same above http://www.t.me/LenScreenOC [MENTION=901293]t.m[/MENTION]e/LenScreenOC ) but maybe they work only on EVO, for me they don't work on xiaomi.eu with any settings, but this one of caballero works good.

5) for safety activate DC Dimming / Screen flickering, no need on xiaomi.eu, but all other roms and dtbo needs it, since 75hz doesn't give green tint at all and since i dunno if it works well on evo, put it on, better if it stays on anyway (sometimes keeps lagging also on x.eu of it's off)

6) go in developers options, untick (put the toggle off) on the option "Disable HW overlay" or something like that, depends on your system/language.

7) try test ufo site on chrome, should give 75fps, dropping to 70 minimum, dont worry about sync messages and errors.... if you get 30/60fps, try for safety and double check with stock miui browser, dolphin browser, kiwi browser, or some other browsers.

8) Try netflix, it probably hangs on and will take till a minute to start, then it should go but doesn't recognize L1/Full HD/HDR, but you should be able to watch with dark screen or error messages, if everything is gone good.

If it doesn't work uninstall netflix, be sure disable HW overlay is off and DC dimming is ON, do not reboot (disable HW overlay must be unticked/untoggled/disabled every time you reboot), reinstall netflix, try again.

9) try yourself user experience and eye perception, if you feel it smoother, it's really only for expert eyes, the difference for normal user is not visible at all, beleave me, better to stay at 60hz and have netflix in full hd, l1, hdr.... but if you feel smoother on 75hz with no frame drops, good battery and working netflix, decide if to stay on 75hz or not.

Now there is people saying they have 90hz working..... and also full hd l1 hdr netflix... will check why, how, on which rom, whats different, what they used etc, but at the moment this is the best solution i found... as you said whatever else i use, whatever rom, kernel, or dtbo, keeps on 60fps or 30fps lagging, but nothing works... only this method/combination of rom/kernel/dtbo/settings gave me as a maximum result a somehow stability on 75hz but still fighting with netflix, dunno how others say they have 90hz working... probably different rom, or maybe they are stil on adroid pie, some aosp rom and immensity kernel and who know which dtbo they are using and which settings, we should cooperate and talk a little bit all together sharing experiences among this thread, immensity kernel thread and general disccusion to find a FINAL ULTIMATE USER FRIENDLY EASY GUIDE.