Unless Uniworld dress code is very different to Scenic dress code, which I doubt - on our Scenic Europe river cruise, jeans at dinner were quite common as were shorts.
It was warm weather (early September) and I estimate aprox 1/4 of the men were in shorts for any given dinner
Not skimpy gym type shorts of course - but regular almost knee length cargo types and similar.
Also t-shirts were commonly worn - again, nice neat ones., not gym wear type ones.
Similar observation to CDNPolar.