switching custom shaders to URP

Hello,

we are currently evaluating the possibility of switching our project to URP from the standard render pipeline.
The obvious first thing to break was the new render ordering because we depend on camera depth to sort our UI and 3d cameras. It was easy to fix this up using the new camera stack.

I was surprised however that most of our shaders were still working as I imagined URP shaders need to written in HLSL. The only bits that were broken were the shaders using lighting, but for example our FX uber shader was just working out of the box. Am I missing something or is there a backwards compababilty for "old shaders" in URP?
While I see SRP batching is not working for those shaders it still would enable us to slowly update our shaders to increase performance.

Thanks for any wisdom!

seb