It was never your ears. It way your auditory nerve.
The auditory nerve runs from your ear to your brain, sitting just behind your earlobe where you can put a finger on it, and its only job is to fire when there's real sound. Years of saws, grinders and gunfire damaged that nerve, and damage doesn't silence it, it does the opposite. The nerve starts firing on its own with no sound in the room at all, and your brain does its job correctly and turns that signal into sound. The ringing is real, the sound isn't, and you aren't imagining it. A breaker that trips has to be reset by hand, and this is the same, which is why twenty or thirty years have gone by without it fixing itself. Every supplement, sound machine and hearing aid you tried failed for one reason, and it isn't that you're a hard case. None of them could reach that nerve.