I haven't noticed a sulfur smell but I almost always use this filter:
https://www.campingworld.com/hydro-l...ter-filtration
That said, most if not all of the places I camp have city water supplies. Years ago I rented a house with a shallow well. The sulfur odor was not so much noticeable after a shower but it sure screwed up iced tea. The research I did then said you couldn't filter it out. It looks like there may be solutions now. Out of curiosity I looked around and found this:
https://www.cleanwaterstore.com/reso...in-well-water/
Most of those systems are large and expensive, probably not for trailer use. Here's another source:
https://culligan.com/home/solution-c...-the-rotten-eg
Since you mentioned showers, is it mostly on the hot water? The second link mentions an anode rod in a water heater can cause the problem. MOst Atwood RV heaters don't have one - what do you have?
Good luck.
Al