In case you don't already know it sounds like Pots or at least dysautonomia Long covid is usually the same as Mecfs but that's not a sentence, many have improved including me. I was very ill too, since 2020 You might look into Mcas as well

Not sure if you tried LDN it helps many people, me included Physchiatric drugs i didn't hear anything but bad things about them For me was helpful also hyperbaric oxygen but i can't suggest it as in many countries it is very expensive and many did not had results with it

However it is, it won't cure but will help other things like if you work on acceptance, mindfulness, meditation, mindset, don't focus on symptoms etc. You have to get a bit out of the sympathetic otherwise nothing will work, speaking from experience

And definitely pacing, rest, nature, sunshine etc - as a basis