Using mixed lighting in Mesh

Thanks for asking about this TAndrieu - you might be one of the first people to try out mixed lighting (we normally go fully baked). To help troubleshoot can you share a screenshot of what you see in edit mode vs. play mode?

I read womewhere that Mesh use it own shaders, but I don't find the source anymore. So, does Mesh shaders supported mixed lighting ?

Mesh allows you to use custom shaders. So, you can use any built-in Unity shader (supported by URP) or write your own. Your shaders get uploaded with your environment at upload time. It is possible a mixed lighting feature you need isn't enabled in the Mesh client rendering settings - which could cause an issue like this.