When are Lens Flares rendered?

Thank you for the hint!

I added in my shader Tags {"Queue" = "Overlay+1"} but it didn't relly work.

Maybe you can test how integrated into Unity lens flares are by creating a quad, assigning a renderer to it with one of the standard light flare textures, then assign the light flare material/shader.

I noticed when you create a lens/light flare in Unity, you Add Component->Lens Flare. But when you look at that game object, it has no shader, material, no renderer, which makes me think it is engrained into the Unity engine.

But if you look under the standard light flare directory, there is a shader and some textures in there, so you could conceivably build your own. If you build your own, and your post processed image takes it into account, then it looks like you'll need to either create your own fully functional lens flare or use Pro Flares or a similar plugin. Good luck!

Alright I'll be looking into this, thank you very much!