Issue with a simple Unlit receive shadow shader

Hello guys, I'm trying to write a basic Unlit shader that would also receive shadows.

The following code (below) works almost as expected, except that I get a weird dark area as you can see on the image attached. Can anybody help me to understand what I'm doing wrong?

 Shader "Unlit/TextureReceive" 
 {
     Properties {
         _MainTex ("Base (RGB)", 2D) = "white" {}
     }
     
     SubShader {
         Tags { "LightMode" = "ForwardBase" "RenderType"="Opaque" }
         LOD 100
     
         Pass {
             CGPROGRAM
                 #pragma vertex vert
                 #pragma fragment frag
                 #pragma target 2.0
                 #pragma multi_compile_fog
     
                 #include "UnityCG.cginc"
                 #include "AutoLight.cginc"
     
                 struct appdata_t {
                     float4 vertex : POSITION;
                     float2 texcoord : TEXCOORD0;
                 };
      
                 struct v2f {
                     float4 vertex : SV_POSITION;
                     float2 texcoord : TEXCOORD0;
                     UNITY_FOG_COORDS(1)
                     LIGHTING_COORDS(2,3)
                 };
     
                 sampler2D _MainTex;
                 float4 _MainTex_ST;
     
                 v2f vert (appdata_t v)
                 {
                     v2f o;
                     o.vertex = UnityObjectToClipPos(v.vertex);
                     o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
                     UNITY_TRANSFER_FOG(o,o.vertex);
                     TRANSFER_VERTEX_TO_FRAGMENT(o);
                     return o;
                 }
     
                 fixed4 frag (v2f i) : SV_Target
                 {
                     fixed4 col = tex2D(_MainTex, i.texcoord);
                     UNITY_APPLY_FOG(i.fogCoord, col);
                     UNITY_OPAQUE_ALPHA(col.a);
                     float attenuation = LIGHT_ATTENUATION(i);
                     return col * attenuation;
                 }
             ENDCG
         }
     }
 }

Any feedback would be much appreciated!