FMN hydrolase that catalyzes the dephosphorylation of flavin mononucleotide (FMN) to riboflavin (PubMed:22002057, PubMed:24123841, PubMed:27490826). Can also dephosphorylate 5-amino-6-(5-phospho-D-ribitylamino)uracil, also known as ARPP (PubMed:24123841, PubMed:27490826). Not required for riboflavin biosynthesis in planta, but may help maintaining flavin homeostasis within chloroplasts (PubMed:27490826). FMN + H2O = phosphate + riboflavin 5-amino-6-(5-phospho-D-ribitylamino)uracil + H2O = 5-amino-6-(D-ribitylamino)uracil + phosphate kcat is 0.59 sec(-1) for FMN (PubMed:22002057). kcat is 2.80 sec(-1) for 5-amino-6-(5-phospho-D-ribitylamino)uracil (PubMed:27490826). Optimum pH is 6.5-7.0 for both catalytic activities. Optimum temperature is 40 degrees Celsius for both catalytic activities. Homodimer. No visible phenotype and no effect on flavin metabolite profile and abundances. Belongs to the HAD-like hydrolase superfamily. DOG/GPP family.