I’ve had this issue for 18 months now since our neighbours decided to let their cats inbreed from 2 > 15~
I’ve tried everything you can think of, now at a stage where the entire front patch of stones has 10 (yes 10) 2mx30cm spike strips covering the lot.
There is one strip where it’s not covered (as I ran out), and they all now **** on that one patch and the stones along the path.
The odd cat turd is fine, having a constant stream day and night from a pack of feral cats (they don’t get looked after properly, half of it is diarrhoea) stinking up the place causes far too much mental torment, aarrrggghhh!!