These are well filed under “might help/highly unlikely to harm.” As always, dose intelligently.
To that list I’d add sunlight. Getting a few minutes per day of sunlight, particularly on the torso or back is very useful for generating vitamin D. I usually try for 20 minutes per day in the wintertime, a little less in the summer, but I have very light skin.
I’ll also add some anecdata: a year or so before Covid, I started megadosing vitamin C as an anti-inflammatory (2-3000 mg daily). It didn’t apparently help my inflammation at all, but I haven’t been healthier in my life from a sniffles/cold/flu/Covid standpoint.
Ivermectin is also “might help/highly unlikely to harm”, at least with a modicum of dosing intelligence, but it is more expensive and harder to get. I’ve heard mixed anecdata on it. Supposedly the newer studies are showing pretty close to no effect. It’s possible that the third world results from ivermectin were a function of cleaning out parasite infections (ivermectin’s on-label usage) improving Covid outcomes.
+1 for weight loss, too, though it’s too late on that for someone who already has Covid.