i exclusively contribute non UI stuff to kde because i could never get the hang of qt.
I'm a weird contributor tho. i only focus hard on one annoyance for a couple hours and convince myself i can code a solution by just looking at the project code... it mostly works but not for kde apps UI.
it doesn't help either that qt (or maybe its a kde thing) keep changing the base ui code. qml, designer, widgets... it's a dozen frameworks instead of one. not to mention most apps are usually in a mixed abandoned-migration state.
well, they just green ligthed a goal to make kde app writting easier. hopefully we will get a one stop place to read how to accomplish things.