Both ears for about, uh, 25 years (I went to a lot of un-earplugged gigs at university in small venues.)
The Neuromodulator from mynoise[1] sometimes alleviates it for a period of time, especially mixed with some coloured noises.
Other than that, there's apparently research indicating that notched audio (music with your tinnitus frequency removed) may help train your brain, e.g. [2].
Annoyingly mine seems to be a broad spectrum and/or my ability to recognise pitch is abysmal which means I've not been able to test this myself - but there's apps to do it for you.
The Neuromodulator from mynoise[1] sometimes alleviates it for a period of time, especially mixed with some coloured noises.
Other than that, there's apparently research indicating that notched audio (music with your tinnitus frequency removed) may help train your brain, e.g. [2].
Annoyingly mine seems to be a broad spectrum and/or my ability to recognise pitch is abysmal which means I've not been able to test this myself - but there's apps to do it for you.
[1] https://mynoise.net/NoiseMachines/neuromodulationTonesGenera...
[2] https://clinicaltrials.gov/ct2/show/NCT04661995