I have also had long covid symptoms, many similar to yours, it mine lasting neurological symptoms and dysautonomia. But I found a pulmonologist, of all specialists, who prescribed LDN- I’ve been taking it for seven months and he said it could take up to 6 months before I got relief. I am happy to report that my fatigue is less, headaches much less, and horrible rumbling sounds in my head, much, much better!
I had been through docs if every specialty, and it wasn’t until my hematologist referred me to his friend who was on the front lines of Covid, helping patients survive Covid pneumonia, did I finally get the help I needed.

LDN, low dose naltrexone, is inexpensive, easy to take- one small capsule before bed- and has been very effective. I highly recommend everyone suffering to try it. It’s used for many medical conditions, but few people know about it. Crone’s disease, cancers(and it helps retain hair during chemo) and many other conditions.
Consult with a knowledgeable doc and make sure it’s prescribed from a reputable pharmacy- my doc uses a pharmacy in Florida. I live in NJ.

There are no side effects that I experienced, and it has been very effective. My symptoms are not 100% gone, but very diminished.

Good luck to all.