Large world and efficient lightmapping

Hello everyone,

I'm working on a project with a very large world and I'm investigating what would be the best solution to use lightmap efficiently (terrain + buildings).
Could it be possible to split the world into small zones that will have their own lightmap and be loaded/streamed as we move around? (World composition style)
AFAIK Unity does not support this feature, so is there any plugin to allow me to do this?

Should I split the world into different scene then merge them at runtime? But then how to handle the lightmap seam between scenes?

I was also thinking to save each zone as a prefab then bake the lightmap of each zone with something like Bakery.
Could that work and would it create obvious seams between each zones in the lightmap?

I'm using Unity 2020.3 at the moment.

I'm really open to any suggestion!
Thank you