I would probably simply rewrite the “setReferrerUrl” to exclude the subdomain string and reduce the URL to the top-level-domain.
Reference: JavaScript Tracking Client: API Reference - Matomo Analytics (formerly Piwik Analytics) - Developer Docs - v3
Written in JS it’s quite close to what hjkatz did here: https://forum.matomo.org/t/ignore-all-query-parameters/14658
For quickly analyzing past visits I’d export to TSV and make some spreadsheet magic.