Potty training child who doesn’t care.

I’m at my wits end I swear. My 4.5 year old absolutely will not potty train. I feel like I have tried literally everything and he doesn’t care. The only thing that even remotely works is putting him on the toilet every 15 minutes but he only pees, won’t poop, and half the time he “doesn’t have to go” and pees the second he gets off. It doesn’t matter if he’s in a pull-up, underwear, or naked. He doesn’t care if he’s sitting in shit and he won’t tell us when he does, we have to drag him kicking and screaming for a diaper change. He has trouble communicating and is in speech therapy but it hasn’t helped the potty training at all. They won’t risk multiple accidents at preschool (not that I am expecting them to) but there’s literally no point in even trying for two days when he will go right back to pull ups at school. At this rate he’s going to be in diapers his whole goddamn life and I’m sick and tired of being judged and assumed it’s due to lack of trying or laziness on my part. I HAVE TRIED EVERYTHING THIS KID JUST REFUSES TO USE THE DAMN TOILET.