It’s difficult!
Wet food is a must to help the kidneys. Bobby had a kidney problem, protein losing nephropathy PLN). And found the Hills and Royal Canin disgusting, they are very bland. My vet gave me some recipes for home made, again bland, and you can google more. There is a Yahoo Kidney Group, which I joined, but it is US based and I didn’t find it helpful because all their meds, test results etc are in different values and scales, and recipes all done in cup measures! Except eggs.
The vets’ prescription foods are ridiculously overpriced when it’s mostly rice, so the PDSA vets were delighted when I donated my leftovers to them.
If I find out any more I will pm you.