I've had MCTD for almost 30 years. I was on Methotrexate for about fifteen years and I was able to work fulltime until retirement. I am not on it, anymore. But--I can say that attending to hydration is seriously important for feeling active. I also take D3 and sublingual B-12. I cannot always do a full day of activity, but I do pace myself with a quiet day before a busy one and an easy day afterwards. Eating well matters also, so avoid processed foods and anything you think you might be intolerant to, like potatoes, tomatoes, dairy, whole wheat and sugar. I do agree that long Covid seems alot like autoimmune disease. This last time, I took Paxlovid and recovery was so much better. In Europe, they treat this with antibiotics, and research here is looking at it. But, it may be that the real thing is minding your microbiome (see Terry Wahls writings).