I’m not sure I understand correctly…
If your uv2 are completely different from one instance to the other you will have to put all the uv2s of all the instances in a texture and use an attribute to indicate the offset in this texture to start reading the uv for each instance.
This may help: Separate value for each vertex for instances? - #2 by Evgeni_Popov
If your uv2 can be deduced from the uv by a simple offset + scale you can just pass this offset + scale as two instance attributes, but I doubt you are in this case.