There are a number of IRB-approved studies by research institutions / universities as well as past/current patient-led efforts from US/Canada, UK, and Germany.
One of the more important studies would be the LISTEN study. It’s run by Yale researchers and has funding by the Howard Hughes foundation, so they’re allowed to research vaccine injury. That team recently collaborated with Mount Sinai in a large Long COVID study (ELI5 summary) which ran research-level tests on patients to look for biomarkers. They found that auto-antibodies weren’t good biomarkers and they also found low cortisol levels.
If you have the time and ability, please consider participating in some of these studies so that we can better understand what’s affecting us and how to treat it. Thanks!