I want to preface this by saying that I did years of vipassana meditation before tinnitus hit me.
I did a mindfulness course for tinnitus. The instructors were capable and prepared. However, this is what would typically happen.
They would say "focus on your breathing, then when your attention wanders back to the tinnitus, once you realize it, make a mental note of that and go back to the breathing." And I, for the millionth time, "I'm not able to focus only on the breathing. The tinnitus is so intrusive that the best I can do is 10% breathing 90% tinnitus. There is no wandering back, I don't have a choice, it is just there, whatever I focus on, whatever I do." And the next time they would go on again with the same instructions. I even tried to make the tinnitus the object of meditation but that is not different from how I live when I do not meditate. I have no choice but being assaulted by this thing.
I ask all the prophets of mindfulness to be respectful to people who can't be helped by it.
Try this thought experiment. Meditate with a radio playing music near you. Maybe music you don't like. 40 dB. You can become aware of your breathing, physical sensations, the music, the thoughts and the sensations the music evokes, and then maybe go back to the breathing, while being aware of the music.
Next try the same thing at 65db. It will be harder. Some will manage, others will be too distressed. Ok, you can sit with the distress, but if you were forced to stay in the room you would be doing the same. No need to meditate. Maybe you can be non judgemental about the music. Maybe.
Now 130 dB. What do you think would happen?
And yes, I have seen the picture of the Vietnamese Buddhist monk burning alive while maintaining a dignified posture. He was great, bigger than life. But not everyone can do that, even with years of training. As I said above, not everyone is the Dalai Lama (and it was meant as a tragic comment and not a funny one, by the way). Mindfulness can only take you so far, and if your tinnitus is truly catastrophic and keeps worsening, it can do very little, unless again you are wired like the Dalai Lama. My friend therapist I mentioned above was a real mindfulness expert. She had spent years in India. She didn't say the Dalai Lama comment as a joke but as a point to highlight the limits of meditation and mindfulness.
If mindfulness can help you with this condition, more power to you, but let's not pretend it works for everyone. The tinnitus level and intrusiveness matter. A lot.