Unity MVP coordinate exchange

I use below code work on mobile protrait, but if set to landscape-left, it can't set right texture on 3d model. i try change P(projection) degree, but also have problem Code:

     // get MVP matrix
                 Matrix4x4 P = GL.GetGPUProjectionMatrix(Camera.main.projectionMatrix, false);
                 Matrix4x4 V = Camera.main.worldToCameraMatrix;
                 // use plane to get texcoords for target
                 Matrix4x4 M = mPlane.GetComponent<MeshRenderer>().localToWorldMatrix;
                 Matrix4x4 MVP = P * V * M;

ShadeLab:

 // calculate new uv in camera image
             float4 uvTmp;
             uvTmp = mul(_MATRIX_MVP, float4(IN.uv_MainTex.x-0.5f,IN.uv_MainTex.y-0.5f,0,1));
             uvTmp.x = uvTmp.x/uvTmp.w;
             uvTmp.y = uvTmp.y/uvTmp.w;
             uvTmp.z = uvTmp.z/uvTmp.w;
      
              // some swap for different coordinate system
             uvTmp.x = (uvTmp.x + 1)/2.0f;
             uvTmp.y = (uvTmp.y + 1)/2.0f;
             IN.uv_MainTex.x = ((1-uvTmp.y)-0.5f)*_xScale+0.5f;
             IN.uv_MainTex.y = ((1-uvTmp.x)-0.5f)*_yScale+0.5f;

i have two question: 1.whether we change the P(projection) can adapter the lanscape-left 2.if the first can't solve, how can i change the shader

(Don't let this issuse dead. balabala....)