DeaDBeeF sort of is similar but doesn’t seem to have the plugins I need to do a proper full-screen 10ft GUI, Facets-like library browsing, surround upmix, DLNA streaming to other rooms etc.

I have to give Krita another try and see if it can import/export .dds, but my impression from playing with it for a few hours is that it seems to focus more on digital painting instead of photo manipulation (which modding textures essentially boils down to). I also have my GIMP workflow down to muscle memory, it only takes me minutes to do eg a recolor or upscale+fake details via sharpening and noise.