Catalyzes the transfer of the 2-phospholactate moiety from (2S)-lactyl-2-diphospho-5'-guanosine to 7,8-didemethyl-8-hydroxy-5-deazariboflavin (FO) with the formation of oxidized coenzyme F420-0 and GMP. (2S)-lactyl-2-diphospho-5'-guanosine + 7,8-didemethyl-8-hydroxy-5-deazariboflavin = GMP + H(+) + oxidized coenzyme F420-0 Cofactor biosynthesis; coenzyme F420 biosynthesis. Homodimer. Belongs to the CofD family.