It came up early on. It is an effective remedy. But others (esp. ivermectin) are easier to get and more effective. There are multiple studies on methylene blue working against Covid, if you search medical journals.

Interestingly, methylene blue is also photo-dynamic, which means that it will save a frequency of light and radiate that frequency throughout the body when it is taken, like glow-in-the-dark material, so it also lends itself to phototherapy treatments. But that's a whole different mode of action. Interesting stuff. Also turns your pee green for a while.