My ex and I took home two female cats who'd lived together for years from cats protection.
We had them 3 years until my ex said enough is enough. Like you, we tried everything however we had to replace 3 carpets, our expensive mattress and some underlay too because it had soaked through.
We spent money at vets, getting plug ins, different litter for the trays, different types of trays, they had cat flap, toys, tried different food/diets, bought them beds, nothing at all worked.
A friend knew of an elderly woman who wanted a cat, the elderly woman knew about the issues and they went to her. I felt like I'd let them down, cried a lot because I felt so bad but got regular updates, they didn't wee in her house, they were happy, content. We got pictures etc.
I have no idea why they took such a disliking to our house, we even moved around furniture.
Emotionally it's draining, physically it's draining, financially it's draining. The smell of cat spray/urine is so so strong it would make my eyes water. I tried scrubbing with all sorts.
Sometimes you have to admit defeat. Overall we were happier and so were the cats. They have since passed away due to old age and I'm glad the final years of their lives they were settled.