Hello,
This plug-in is performing an hardcoded URL normalisation of GUIDs from https:// to http://:

But the articles themselves in the corresponding RSS feeds have GUIDs using https://.

This leads to duplicate in clients subscribing to those feeds because articles exist with two different GUIDs:

FreshRSS/FreshRSS#5151 (comment)

At the very least, the normalisation should be made the other way around, now that a majority of WordPress blogs run HTTPS, including WordPress.org, but a better approach would be desirable.