As some of you know, Mesa 25.1 recently implemented this protocol, which allows HDR to be used on Wayland without the issue of washed-out colors mentioned in this post.
This addresses the problem at its core, eliminates the need to use vk_hdr_layer (which is no longer supported by all distros, NixOS for example recently removed it from its package repository) and would represent a significant step forward for HDR gaming on Linux with the major GPU manufacturers adopting the necessary protocol to make it possible, thus also accelerating the stable arrival of Wayland support in Proton (especially now with the custom versions of Proton that allow it to try).
Cheers.