The problem is that the keywords for MainLight Shadows, in the ToonShading subgraph, are incorrectly set up. They are currently set up as two separate shader features, one for MAIN_LIGHT_SHADOWS and another for MAIN_LIGHT_SHADOWS_CASCADES. These need to be removed.
Then an enum keyword needs to be added to the subgraph, set as a multi_compile with _MAIN_LIGHT as the reference value. Then the three enum values should be OFF, SHADOWS and SHADOWS_CASCADES. With that you have made an identical keyword structure (except for Screen Space Shadows) to the ones used in URP's Shaders.
There is also an issue in the Toon shadergraph, used in the project, with how shadows are being calculated. Using a default URP Lit or a Lit ShaderGraph does not produce the same issues.