It's not true that "you cannot get B12 from plants, period" [1]. You can get trace amounts from various edible land plants, but dietarily significant quantities

It's not true that "you cannot get B12 from plants, period" [1]. You can get trace amounts from various edible land plants, but dietarily significant quantities from some algae. Also fermentation of some plants can provide B12-rich foods. It's fair to say that vegans need to take particular care that they get sufficient B12. 1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4042564/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4042564/