My cousin was doing research into chronic fatigue syndrome (which shares a lot with some versions of long covid, and still isn’t ‘solved’) back in the 1990’s. It’s going to take time.

Edit: “Today, the National Institutes of Health launched and is opening enrollment for phase 2 clinical trials that will evaluate at least four potential treatments for long COVID, with additional clinical trials to test at least seven more treatments expected in the coming months. Treatments will include drugs, biologics, medical devices and other therapies. The trials are designed to evaluate multiple treatments simultaneously to identify more swiftly those that are effective.” - source