Plasma on Wayland does have HDR support now… But I don’t have a way to test how good it is, and I think it’s both still unfinished and severely lacking support from applications. But hey, things are improving!
I wouldn’t count on Adobe support though.
I feel like you’re doing something wrong with the nullables… I’m pretty sure you don’t need to mark up files, you can just enable it on the whole project? I’m not sure about the attributes, you might have a point there, but it just makes sense for value vs reference types IMO, since value types are already implicitly different in terms of nullability.
But yeah, I can imagine it’s half-baked, since nullable reference types (that’s the name, previously reference types were just nullable by default with no extra features) are a more recent addition to the language, one that wasn’t built with them in mind.