How to filter data in link field on script report filter field?

Create your filters in the client code, not in the filter table.
Add the script below:

frappe.query_reports['report_name_here'] = {
    "filters": [
        {
            fieldname: "fieldname_here",
            label: "label_here",
            fieldtype: "Link",
            options: "doctype_of_link_here",
            filters: {
                "fieldname_in_link_doctype_here": ["operator_here", "valuefield_here"]
            },
        },
    ]
}

Make sure your reload page report before review

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