I’d be grateful for some guidance on the best way to fix a leak from my toilet. The leak doesn’t come from the toilet so presuming it’s the seal next to the floor and involves the 4inch waste pipe. I am replacing the toilet anyway and presume I need to replace some kind of flange at the base, just not sure what to buy / best way to go about it. I’ve included a picture to help. The old sealant is brittle like crumbling mortar. Many thanks for any advice.