The DSM is your friend ― while it’s arguable that there’s cultural bias involved and you can certainly start a discussion about medicalization and the harmful stereotype of “normal”, it does work as a helpful thing for someone who’s willing to read a lot and needs a place to start and wants a compiled thing to look at and navigate through. You can find it on pdf online.
If you want something more specific, SciELO offers open scientific data about a lot of things, you just gotta be a bit creative with your keywords for research and you’ll have a lot to read about. I’d recommend it for anyone who wants a more hands-on approach on dealing with psychological issues, ripple effects, social struggle, therapy and whatnot.
On the same note, JSTOR is more or less the same as SciELO (if not a bit more wonky on the visual side), and it offers plenty of database to navigate through, on the same note of keywords and search.
I’ve had many people tell me some of Kat Napiorkowska videos on mental health have helped them understand things better, but I’d advise caution, as some of them can be triggering and/or upsetting.