I know that L-Lysine is a good supplement for those suffering from cold sores / herpes. It keeps away outbreaks, so it affect viruses in some way. A relative would get cold sores when stressed, and her old time Dr told her to take them daily, which she does, so she usually goes a year or more without getting one.

Another tool to experiment with. If this fake pandemic has done anything useful, it has increased the world's awareness of treatments to fight cold viruses.