The brute force approach, based on the information you’ve provided, involves creating an array of 256 monitors equipped with analysis ports. These monitors will connect to 256 instances of your coverage collector. Each monitor can probe your modules’ signals using one of the methods outlined in this paper: Updated Example Code from DVCon Paper: The Missing Link: The Testbench to DUT Connection.
By default, the coverage you defined in your collector is collective. However, you can change this to individual by setting the option.per_instance=1 when declaring your covergroup.