This is a paid asset, but now you can download Double Sided Standard Material (Mobile Ready) for FREE, Please keep in mind this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
Double Sided Standard Material (Mobile Ready) v1.0
Transparent materials is supported. You can use textures with alpha channel to make two sided meshes like leaves or grasses.
All shader parameters are like the standard shader.
Important notice: This shader is only compatible with Built-in renderer pipeline. It does not work on URP !
This is a modified version of Unity standard Material that could be used to render both sides of a mesh. It can be used on all platforms(devices) and on Built-in renderer pipeline.
Compatible with Built-in renderer pipeline
High performance on any devices
Has the same properties as the Unity standard shader