PLOS One (stylized PLOS ONE, and formerly PLoS ONE) is a peer-reviewed open access scientific journal published by the Public Library of Science (PLOS) since 2006. The journal covers primary research from any discipline within science and medicine.
I found 2 red flags: One is advertising (https://plos.org/advertise/) and the other one is data collection (https://plos.org/privacy-policy/). Makes it a trade based service. You trade your attention and data to access the scientific journal.