@db72
Sue, I'm sorry to hear about the long-term travails you've had over the decades!
I'm just a few years younger than you, and likewise came down with the "yuppie flu" back then. Fortunately, it lifted of its own accord after about two years. It started with a fairly normal-seeming flu, but just left that fatigue. I spent a lot of time at a university. library researching Medline, etc. at that time. The Epstein Barr theory did come into vogue then, but I don't believe it's ever been truly confirmed. In fact, it seems as though multiple viruses, such CMV, EBV, and HHV-6, are often observed to be reactivated with this syndrome. I do believe that CFS/ME and LC are the same phenomenon.
My own hunch has been that this is a failure of some peoples' immune system--likely genetically determined as you referenced--such that it stays "stuck" in a heightened state that leads to the array of symptoms we experience. I'm not convinced that any of these viruses (Covid-19 included) are themselves the sole "culprit" for our long-term reactions.
Now that I've had LC for a year and a half, it feels much the same as the CFS I had back then, fortunately confined to that sole symptom.
I "plan" for it to lift in the coming summer! Meanwhile I'm just treating it symptomatically with prescribed amphetamines, with uneven results thus far.

It's dismaying that so little progress has been made on this/these disease(s) after DECADES!
Maybe 2026 will be THE year, no?