Neutered male cat pees on everything

I’ve read a bunch of posts like this but none have really helped with my specific situation. My mom is at the point of trying to rehome him because of this and I don’t know how to stop it.

We got him about a year or so ago from the streets, no idea where he came from or even how old he is (vet thinks around 2y/o but not completely sure). He’s a very very sweet boy but he didn’t get along with our other 2 (both male and neutered) cats at first, but they have grown to be friends. They still fight from time to time, but I have no option to separate them other than re homing.

When he first started peeing on stuff (he also pees and poops in the litter boxes), we took him to the vet to get his age, test for UTI, and they gave us some advice like enzyme cleaner and the litter that attracts cats which we tried all of that and more.

I don’t think it’s a bladder issue because he will walk right in front of us and pee on it a little bit and run away when we get up, like he’s doing it for attention almost. But other times he will pee in my closet or something in private and I won’t know until later.

If anyone has ANY advice, I’d love to hear it. I want to get him back to the vet but I don’t even know what to say and it’s so damn expensive so I want to know what to ask for beforehand. Thanks in advance.