That has already been discussed before, you simply can't add HDR info out of nowhere on source content that is purely SDR, like all GameCube/Wii games. Even if that "Special K" thing can make your TV switch to HDR mode, games you run through Dolphin still won't have any HDR info and, at best this program will apply some generic tone mapping on top of the SDR output of the games and that's all. That's not HDR, I dare to say whatever improvements you're claiming are pure placebo effect and the same results very likely could be obtained by messing with the color and gamma settings of your TV while in SDR mode.
Edit: this post summarizes why HDR isn't a thing on Dolphin very well. Although a little old, that whole thread still has relevant info.
Edit: this post summarizes why HDR isn't a thing on Dolphin very well. Although a little old, that whole thread still has relevant info.
Avell A70 MOB: Core i7-11800H, GeForce RTX 3060, 32 GB DDR4-3200, Windows 11 (Insider Preview)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)