I happen to know a few folks who work in this field (detecting fraudulent scientific papers). This is a bit of an insider knowledge, but there are science sleuths who are fearing for their lives... there might be some seriously shady stuff going on behind research paper mills, but I don't know who will be the one digging those up.

If it is just on an individual level though methinks Retraction Watch does a decently good job at informing what might or might not be trustworthy

A recent report on Retraction Watch, a PhD student was trying to figure out who's behind a papermill: https://retractionwatch.com/2024/10/01/hidden-hydras-uncovering-the-massive-footprint-of-one-paper-mills-operations/

This is from Nature News today: https://www.nature.com/articles/d41586-024-03427-w. Heard a bit about this startup even before so...