I think @Hyde might have something to add, about kidney supps.
Yeah blood pressure control is the top dog - prevention.
I have gotten to talk with all of the guys who have won America’s Strongest Man under 231 the last few years (you have to be a 231 Pro Strongman just to enter that show). These guys usually get as big as 260-280 offseason before getting ripped and cutting 20-30lbs of water to make weight. They are pushing everything. Something that made an impression on me is hearing one say “the length of a pro strongman’s career is directly tied to how long his kidneys can hang on”.
I know Dante has said the minimum daily amounts he has seen be genuinely effective is 3-4g daily, which is what he recommends to someone trying to improve numbers. In some extreme kidney damage scenarios he’s known guys to get more results going up as high as ~18g daily, but these are extremes he had heard of.
Pycnogenol at 100mg per day is something he recommends as well, and if you look at Nephrogen and Revive’s kidney product they both use pine bark extract as a cheaper alternative. Beet root, and anything that lowers bp and improves bloodflow will be helpful. That means things like nitrates (Vasoblitz), tadalafil, garlic, nattokinase, curcumin, hawthorn berry, grape seed, controlling bloat on cycle via diet and AI if needed, STAYING HYDRATED, doing routine cardio. Using Lisinopril or other script meds is much healthier as far as I can tell than damaged kidneys from high bp.
Probably many more things to try, but the gist is keep hydrated, keep bp down however you need to, stay active, exercise on top of your training, control bodyweight (lean at 220 is worse than fat at 220, but still much healthier than a fat 260 with the lean mass of the 220).