I don’t have personal experience with post Covid symptoms. I have been taking CO Q10 200 mg daily for years with no ill effects after researching
the benefits in the medical literature.
It is not FDA approved for any particular disease though allowed as safe OTC.
There are positive studies for its use in statin myopathy and fibromyalgia
and chronic fatigue patients. It has some possible helpful effects in mitochondrial diseases and can act to reduce some inflammatory parameters in rheumatic conditions.