Anecdotally, I can only speak from my experience getting severe pneumonia (I barely managed to avoid being hospitalized), but I think it's worth considering that since COVID is similar, and it's also similar to HACE/other high-altitude diseases (because of its huge impacts on blood oxygen levels) that much of 'long covid' is likely the long-healing process that follows those sort of diseases.

Speaking for myself, it took me about 6 months to be able to walk up steep hills or stairs without needing to pause or becoming incredibly winded. I had malingering symptoms of the disease for months afterwards. They eventually went away, but I presumed they were likely just the result of getting wrecked by pneumonia.

What i'd be really curious about...what does the recovery for folks who develop severe altitude sickness, edemas, etc look like? As I understand it's pretty brutal at the moment, but no idea of the long-term.