Source (in French): Djokovic rend visite à un gourou qui affirme que “ses” pyramides ont un effet curatif sur le Covid-19
What do you guys think about it, could it be true? We should all head to Bosnia?
This study was likely a logical fallacy, though (Argument from ignorance - Wikipedia). Low sample size with a false positive based on a correlation without cause-effect relationship (although the observed effect, despite being pretty dubious in its diagnosis, may have been due to the effects of the lockdown or the overly fear-inducing media coverage).
Here is a page on WebMD (created by the West) that pretty much agrees with the belief of the healing properties of negative ionsHe assumes that negative ions are the greatest enemy of the coronavirus and that the concentration of these ions is particularly high in the Vissoko pyramids. In images provided by AP, he shows Djokovic his so-called ion counter. "Look, we have a very low concentration of just 210 negative ions here," he explains to the Serb.