Shader "Hidden/Shadow2DShadowSprite"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Color("Tint", Color) = (1,1,1,1)
        [HideInInspector] _ShadowColorMask("__ShadowColorMask", Int) = 1
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }

        Cull Off
        BlendOp Max
        Blend One One
        ZWrite Off
        ZTest Always

        // Process the shadow
        Pass
        {
            Name "Draw Sprite Shadow (R)"

            ColorMask R

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 vertex   : POSITION;
                float2 uv       : TEXCOORD0;
                float4 color    : COLOR;
            };

            struct Varyings
            {
                float4 vertex   : SV_POSITION;
                float2 uv       : TEXCOORD0;
                float4 color    : COLOR;
            };

            sampler2D _MainTex;
            float4    _MainTex_ST;
            float4    _Color;

            Varyings vert (Attributes v)
            {
                Varyings o;
                o.vertex = TransformObjectToHClip(v.vertex.xyz);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.color = _Color.a * v.color;
                return o;
            }

            half4 frag(Varyings i) : SV_Target
            {
                half4 main = i.color * tex2D(_MainTex, i.uv);
                return half4(main.a, main.a, main.a, main.a);
            }
            ENDHLSL
        }
    }
}
<URP>/Shaders/2D/Shadow2D-Shadow-Sprite.shader full source
