Awesome topic! We use Anti-Icky Poo for cleaning up inappropriate cat urine. Anything else we've ever tried leaves a residue behind that the cats can smell (I assume) and encourages them to continue using that spot.
But your question got me wondering about a DIY solution.
This article at The Spruce was a useful discussion in general, but also included:
How can I make a homemade enzymatic cleaner?
...
Add four parts fruit scraps, eight parts water, a teaspoon of yeast, and one part brown sugar to a canning jar or soda bottle. Stir to combine, cover, then let sit in a dark and cool place for a month. Make sure to unscrew the top daily to release any built-up pressure.
and now I want to try that...but isn't it just weak live vinegar?