Tracking multiple sites and suppliers

I have multiple websites with different domains. On each website a number of different suppliers have their products.
I want to use only one tracker ID for att websites and be able to show each supplier how their products perform on each website and in total.
Like Google Analytics, how can I seperate the data based on domain? Only changing the Title is not enough, it has to be a more solid way.

Hi Matt
Thanks for your reply.
If I set up one account for each supplier, how do I track domains?
It’s importantly that the supplier can see how different websites perform.