Currently Gwenview, Digikam and Spectacle all lacks proper wayland color management protocol support, making them unable to support wide-gamut or HDR images.
This is a kind of general Qt app issue at the moment. I don’t know what it’s like for GTK apps.
The only way a Qt app can show anything with HDR is to have a separate Wayland surface (something window-ish) for the HDR content or to have the whole app window in HDR. The former is difficult to integrate into a lot of existing apps and the latter will make UI colors look wrong. If all an app needs to do is show HDR content, that can be done, but most users expect nice UIs with various features too. There is work being done by Qt and KDE developers to deal with this issue, but I’m not sure when it will be solved.
At lease we need wide-gamut SDR support.. Which is already supported by Qt.
Color management is one big issue that often gets categorized under HDR even if it’s technically not all HDR.