@davidrevoy Thanks for the detailed post!
What's wrong with the Flatpak package for Krita?
It's Verified on Flathub, which means it's officially maintained by Krita's developers. It's linked as a download option on the Krita site. Though it says "Maintained by the community," which is strange.
The Color Management & HDR Wayland protocol seems close. They seem to be waiting for implementations. See this Mesa draft MR from last month: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28762
& Weston: https://gitlab.freedesktop.org/wayland/weston/-/issues/467