I hear you.
I have been able to skirt the burnout line and still remain _somewhat_ effective. Given that I'm still(for the time being at least) far more productive than my peers it doesn't show. However, I know what I'm actually capable off and I can tell I'm in a "degraded" state. So, I can relate.
Burnout, as I understand it, is a mismatch between your environment and yourself. Like you said, the work is completely unsuited to you. Your brain knows this and is throwing a fit so you will listen.
The way I've been able to skirt the line is this. I know that my problem is that at my job we are chock full of execs that are just trying to justify their own existence and love their voice and very little gets done anymore without a whole lot of pointless meetings. So, given that I can't really _do_ something meaningful anymore(at least not in a reasonable amount of time), I focus outside of work on things that I can actually do. I have a very long list of personal projects and I've been knocking them off my list with unprecedented speed. This has helped me feel _some_ sense of accomplishment, and has staved off the worst effects. For now.
So, if you want a short-term "fix" that may help you get some energy back, figure out what it is that you hate about your environment and see if you can refocus that elsewhere. Easier said than done, it took me some time to figure out that I missed just being able to do things.
That will not help you long term. If what you have truly is burnout, it will not change until your environment changes. In this case, your job. And I'm not necessarily talking about the company either. If you don't like what you do, doing the same thing in another environment will not help.
Now, all of the above assumes you really have burnout. If you do not, what you need will be completely different.
ADHD is not often diagnosed in adults. It doesn't mean it cannot be diagnosed, just that most diagnoses happen in children/teens. Adults that are high functioning will have coping mechanisms for untreated ADHD, some of these may be really unhealthy. One of the hallmarks of ADHD is executive function issues. Can you start tasks fine? Because if the problem that keeps you from finishing tasks at work is that you can't even bring yourself to begin working on them, that could be ADHD. And you can have burnout simultaneously. ADHD + burnout is an explosive combination. One already has issues starting tasks even during "normal" times, now they are burned out, which even for a neurotypical brain makes them unable to start any tasks.
Since you said "psychologists", plural, I'm thinking you got multiple ADHD diagnosis from more than one doctor. So I would start listening to that if I were you :) You can ask for differential diagnosis, as there are some issues that look like ADHD but are different. It could be "just" burnout, but you won't really know unless you change your working environment. If it is ADHD, you get medicated, and now things improve, it's a pretty good indication that you didn't have a neurotypical brain your entire life. You can still be burned out, in which case it means the coping mechanisms you developed for ADHD got overwhelmed.
Also, do not forget the basics. Your body must be healthy - do a checkup if you haven't done one in a while(that includes dental and vision). Get some exercise, don't have to be strenuous, just keep your body working. Get plenty of sunlight. Make sure you are sleeping well. And eat healthy. Lose weight if you are overweight (that's actually important for mental health, related to hormones and inflammation). None of that will fix your issues, but if you don't even have that covered, you will have a much harder time making any progress.
... I apologize for typing too much. I'm currently struggling myself and I have had plenty of time to think and research it. I know what I must do (get a new job). Having the energy to do some leetcode after work is a different matter.