There are two plants that jump to mind as maybe helping against Covid symptoms. First and most promising, Devil's Club, Opplopanax Horridum methinks is the official name, native to the Pacific Northwest America. Possibly some types of prickly poppies may be worth looking at.
Any attempt at finding a plant or other biological substance that helps against Corona is a shot in the dark, but odds are, if not in the plant kingdom, then from algae or even venom there are plants that can help against this plant if not cure it.
Devils Club was used by the Native Americans of the Region for treating Respiratory Diseases, and some claim it can cure TB, (although there are purportadly many plants that can do that. It also lowers blood sugar. It is the most important medicinal plant of the Natives in the region.
Is there a better forum for people to share plants that may be able to help along with research and outcomes from their uses against this new killer virus?