if i apply lightmap i get this result :
https://i.stack.imgur.com/EaJRu.png
Lightmap Preview :
https://i.stack.imgur.com/JUmZ1.png
Lightning Settings :
https://i.stack.imgur.com/OGjOd.png
I don't know if it's related to the material, but I'm putting the screenshot here anyway :
https://i.stack.imgur.com/r1cgz.png
I'm also using Unity version 2020.3.12f1 and URP v10.5.