COVID would be a rather poor weapon since it's simultaneously not deadly enough to incapacitate an enemy and too contagious to avoid blowback without completely locking down at tremendous economic and political cost (which China attempted to do only to fail when Omicron came around).

If you wanted to make a bioweapon with modern technology and modern understanding of genetics you'd make something super deadly with somewhat limited contagion or even better keyed to biomarkers that are uncommon in your own population. China could do this effectively since it's ethnically more homogeneous than many other countries. COVID is none of these things.