I remember reading somewhere a Doctor found a way to 'cure' ringing in the ears temporarily for almost a year in some people by doing something with a tuning-fork.
But after that article I heard nothing more. I just looked it up and seems it may not be a reliable method.
I have a coworker that swears by certain sound baths to remedy his tinnitus. It “cures” him for 10-12 months and then he just goes back.
Don't know about the tuning fork one, but there is a method where by if you poke some muscle on the back of your neck repeatedly, it stops for some people. This is apparently due to that muscle being the thing that makes a noise, and poking it eventually physically exhausts it temporarily. Obviously that only works if that's your cause.
I vaguely recall that tuning fork remedy as well
I can play a pure sine wave tone with a tone generator app, and dial the frequency up until it precisely matches my tinnitus. I originally did this just to determine that frequency.
But I noticed a side-effect: if I then turn off the tone generator, my tinnitus would disappear! Unfortunately that effect only lasts for a minute or less, so it is not really practical to get relief this way.