28mm rf lenses can be pricey. Also you have to think about how you will compose and shoot. Many won't have nice built in magnification/ frame lines for 28mm and something like the zorki would need an external finder. Not a big deal if you are used to the focal length you can wing it guesstimating. CV ltm lenses seem to have good reviews and price/performance so that can be a starting off point for research. The older canon ltm 28s are very nice and compact as well.