Is lichen permissible for use in Vitamin D tablets, and does gelatin of unknown origin in medicine affect its permissibility?

Lichens are symbiotic organisms between algae and fungi, varying in color and use. The basic principle regarding things is permissibility and lawfulness. There is no religious prohibition against consuming lichens unless harm is proven, based on the general religious texts that permit good things, and the saying of the Prophet, peace be upon him: "There should be neither harm nor reciprocating harm."