After maybe 8 months of this we somehow decided to do a low-Fodmap diet (I participated for support). That included cutting out gluten and dairy (except butter). She healed right up. When we were re-introducing foods, for whatever reason, mushrooms and garlic both had negative effects, and we ended up keeping both out of our diets for a couple years.
Anyway, that's all to say I'd recommend people seriously look at their diet and try to spend a month or two doing low-fodmap if they're chronically suffering from long Covid. Worst case it doesn't help.