This site may be of some help.

I haven't had a cat with kidney disease yet, but have used the Pet Wellbeing liquid gold formulas for arthritis, itching, and thyroid support with great success.

Here is the link to the kidney support one. https://petwellbeing.com/collections/kidney-disease-cat#

We dealt with this a few years ago. Our vet also recommnded the prescription diet which my cat hated. There is tons of info on the internet and CRF kitties including some very active posting boards.

Tanya's CRF Board

As I recall, there is another school of thought that more important than lower protein is lower phosporous levels in the food. Given that mine wouldn't eat the Rx diet, I went this route. I used this food chart to pin down phosporous levels, keeping it as low as possible (this chart was also a lifesaver for our other diabetic kitty)

Food Chart

As I recall, we kept his CRF decently under control for a couple of years. Unfortunately he also developed high blood presssure, went blind, etc. But he made it to 19!

Read all you can and remember that you know your cat better than your vet. I always appreciated input but I had to make decisions based on my own experience with my cat.