Sorry its hard to know if this is a related issue. I also get the ‘blocky’ lights with URP forward+ (unity 2022.3.11f1). In my case its a point light rendering to a RenderTexture. Directly to monitor does not give these artefacts. And the artefacts are different when using different RenderTexture resolutions.
In the places where the light is drawn it looks like the propper color, but its just completely discarded on the other pixels. From URP Forward+ (Tiled vs Clustered) it seems the forward+ lights are binned in ‘tiles’, could it be these tiles are not binning right? Resulting in ‘seeing the tiles as pixel like artefacts’.
Did you manage to improve your situation?
Edit: when overlaying the ‘Lighting complexity’ in the Rendering debugger-> material override. It seems to be related to the result.
Edit2: When I match my RenderTexture Resolution to the resolution of my game window this issue goes away for me.