aheid,
I agree with your perspective that "they" are making assumptions on a great many things. Unfortunately, too many want us to think Covid, Covid vaccines and post covid issues are settled "Science". And they are not.

Having said that, the science has to start somewhere and those observations that provide direction towards solutions can take time. To be fair, getting to a Polio vaccine, antibiotics, heart transplants took years to get to. I wish it were different but I have to reset me expectations so I am not constantly frustrated as it relates to how long this will take.

I dont have any specifics on what you should do. What I will share is what has worked for me.

I was offered many of the same exercises that respiratory therapists and a few of them worked. But not all of them and not enough of them so I am on this journey of recovery by myself. Or let me rephrase that to say I am no longer looking for someone to tell me the solution. I am my own best health care advocate and if someone in the medical community does not have an answer, with all due respect to them, I am moving on.

The approach I am on seems to be working for me and the following is my thought process.

1. what is my lung capacity? When I first got out I could not inhale past 1500 on the little breather thing. I kept at it and now I max out that little plastic thing. No one told me, including respiratory therapist, on how to increase it other than do it once an hour. What I learned from the athletic community is that if you inhale to your max and hold that breathe for about 3 seconds and then gently exhale that can help stretch your lungs. At least it did for me.
2. "how" am I breathing? Another thing I picked up from an elite athletic trainer(prof cycling team doc) is that there is "belly" breathing and "chest" breathing. They train the cyclists to maximize both. So I gave it a shot and it did make a difference for me. At first it was not a lot but it was part of the solution so far. The "belly" breathing starts with inhaling through my nose at a moderate rate making sure that the inhalation comes from pushing my belly button out and NOT expanding my chest. Hold it for 3 seconds and blow out in a steady stream through you mouth sort of like you are blowing out birthday cake candles. When exhaling work on pushing your belly button back towards your spine and hold that for 3 seconds.
For "chest" breathing I was directed to do almost the same thing but hold my stomach still and expand my upper chest and rib cage to the point where it felt a smidge tight or uncomfortable. Hold, exhale through my mouth as mentioned above. Breathe in and out like that for a few minutes for each set. It may sound crazy but it helped and now I can do more of them.
3. How much breathing is required to keep my heart rate at a constant level? I got this from a general physical therapist.....After being sedentary I am not as "fit" as I was. The recommendation was that I do more cardio training. At first it started, for me, walking around the room until I was winded. I then got my oxygen thing that goes on my finger that gives me blood oxygen levels and heart rate. The physical therapist gave me a general set of expectations on how I would improve. I am not too proud to say when I walked around the backyard the first few times my heart rate was at almost 130. But I kept at it never letting my heart rate get above 130 and a month later I walked a full mile at 5300 foot elevation. Next step is to do an exercise bike and keep improving. Overall fitness is a big part of this portion
4. I am just starting to understand some of the more sophisticated ways improving my ability to not be so winded. Most of this is outside my knowledge yet but almost all good endurance athletes use these. I think my next step is to get a heart rate monitor that I can wear while exercising that does not fall off my finger. The conversations so far are around things like max oxygen uptake, etc.

Not sure if this helps but just because there is no true "science" out there yet I refuse to believe I cant get better. I want and deserve the life I had before my vaccinations and subsequent week long Covid hospital experience.

I hope in some small way the above can help and that my writing is not too confusing. Dont give up and remember that there is, as far as I can tell, no real science around most of this. We are really to early in that process.

Best,
Mark