Don’t be discouraged, my hound is just like this. No matter how many times I work on it he will heel and when releases go right back to the end of the leash. As if he’s walking any faster there than he would be on a slack leash.
My hound has basically no hair on his belly so when I got the front clip harness I also got a fleece to line the belly strap and it’s awesome. Don’t buy one that’s advertised for dogs because they will be $20+ for a thin piece of fleece. If you get a horse halter fleece cover it will be like $4 and the fleece is thicker/more durable (Amazon link).
I’ve also tried everything and the only thing my dog respects is the head collar because he fights himself more than me. But having treats with me on most if not all walks is also super handy. It might seem like treats aren’t a practical long term solution, but if you work on it solidly for a few weeks/months and keep up with the positive reinforcement of “being next to me on a slack leash gets you treats” you should hopefully see some results and can slowly fade out the treats. The key is consistency. Good luck and if you find something else that works let me know!! lol