How do I get a directional light to work on Mobile?

I’m trying to light a scene on Mobile with directional lighting. With a single directional light, everything renders in complete darkness. Lighting only works with a Skylight, and even then doesn’t seem to properly represent changes in intensity. My main goal is just to get a directional light to work as a first step in making my scene look passable.

My scene has quite a high volume of low poly meshes, but very few textured materials. Most are flat colours without any specularity or transparency. I’d like to focus on using lighting to get the right feeling for the visuals, but it seems like lighting is extremely limited on mobile, at least by default. How flexible are these limitations if you are comfortable with limiting the compatible hardware?

On a side note, I have a water material that uses distance fields to change the colour where it intersects with land, and this material doesn’t draw at all on mobile. Is distance field data not usable on mobile devices?

Someone here states that “cast shadows” must be enabled.

did u find a solution plz if so tell me