@kessme I hope I can offer a suggestion. You might want to have a physical therapy evaluation, and I would recommend a PT who also has the John Barnes myofascial release training. Surgeries leave internal fascial scar tissue that tighten up and can keep the body from moving properly including your chest wall. All the ribs and muscles need to be able to expand properly which creates a vacuum that allows the lungs to expand fully. If anything impairs movement of the rib cage, it can impair breathing. I do have asthma and thoracic outlet syndrome which causes neck and chest tightness under the collar bone where the nerves are passing on their way to the lungs. There are different nerves involved in breathing for the upper and lower parts of the lungs. What happens to me when I can't expand one side of my ribs fully is that I start using neck muscles to breathe which also causes some anxiety and a faster heart rate. When I have allergy and asthma problems it all gets worse, and I can be prone to lung infections if the phlegm gets trapped because my lungs are not moving enough from this physical problem. I do have tightness that extends through my rib cage to my pelvis and does affect my diaphragm movement sometimes. My physical therapist does releases on those muscles, and on the tight muscles near my collar bone and arm pit, and it gets my rib cage moving better, and immediately my breathing is deeper and from the diaphragm. I also do similar stretching at home to keep working on it, and I have lowered my heart rate and slowed my breathing by releasing the muscles between my neck and chest. I am also a cervical spine surgery patient, so I have some scar tissue near this area that will tighten if I don't keep working on it. I know I have a habit of sleeping on my right side, and my body is too tight on the left, so I have been reversing this to try to stretch out my tight left side. I think our habits can contribute to things like this.

Thoracic outlet syndrome is more common than doctors think it is, and most doctors don't understand it because it isn't covered well in medical schools. Sometimes they don't consider a physical problem and how that might cause symptoms. It is worth asking a physical therapist about it, and tests for it will be Doppler imaging to see if the blood supply to the arms is cut off by raising the arm or with a change of head and neck position. Neurologists can diagnose it. Usually physical therapy is recommended for TOS. Doctors who understand it are usually at interdisciplinary medical centers like Mayo and it will be listed as a condition they treat. You might find that physical therapy will help even if you don't go through a lot of diagnosis. MFR works on tight muscle and tissue all over the body and once you learn how it works, you will be able to do a lot on your own at home. The therapist will be able to feel the tight pathways through your body. In my experience, doctors don't usually check for this with their hands, and in medical school, they study stiff cadavers, not living fascial tissue that moves even with restrictions.

Here are some links that may be of interest. I have also included our discussion on Myofascial Release that has a lot of information on where to find information and MFR therapists.
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/
https://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/symptoms-causes/syc-20353988
https://www.painscience.com/articles/respiration-connection.php
https://trainingandrehabilitation.com/how-truly-treat-thoracic-outlet-syndrome/