OnRenderImage does not work in URP. If you are using it to apply image effects with Graphics.Blit, In 2022.2+ should use the Fullscreen Pass Renderer Feature and Fullscreen Graph - or custom shader including Blit.hlsl. Use the Vert function as the vertex shader and call FragBlit in your fragment shader. For prior versions, can use my Blit Renderer Feature. For effects that require more than just a Blit, may need to write your own Custom Renderer Feature - my post on them may help (aimed at 2022+).