Credible accusations reported by several mainstream outlets. There doesn't have to be an official UCI investigation. 

Mechanical doping, performance-enhancing drugs, undocumented medications, and other widely recognized forms of doping all count. 

Note (7/18/23): since I have my own views about Vingegaard (I suspect he's doped and more so than others), I will bet accordingly, and there is an element of subjectivity involved, I will ask an independent trustworthy-ish user to resolve the market for me.