Catalyzes the hydroxylation of two positions of the aromatic ring during ubiquinone biosynthesis. a 2-all-trans-polyprenylphenol + H(+) + NADPH + O2 = a 3-(all-trans-polyprenyl)benzene-1,2-diol + H2O + NADP(+) Cofactor biosynthesis; ubiquinone biosynthesis. Belongs to the UbiH/COQ6 family.