In unity 2018.2.16 i tried to apply a pbr shader to a material, but i cannot do this without converting every mat to LWRP, I do not want to upgrade every mat to LWRP, because it makes some of my other materials look crappier.
I’m confused by what you’re trying to do. Are you trying to make a shader using the new Shader Graph and use it with the built in render path? You can’t, the Shader Graph only works with the LWRP and HDRP, and to use either of those requires replacing all of the lit materials in your project with ones compatible with those pipelines. If you want a node based material editor that works with the built in forward or deferred paths, you’ll need to purchase Amplify Shader Editor from the asset store.