Books. Every single masterpiece that was printed before... a certain date (it will depend the country you live in), is available for free online. They are not just 'free', they're concentrated thoughts/cleverness/creativity available to anyone willing to take the time and, sadly nowadays, to make the effort of reading them.
Not really public domain but close enough: public libraries, most of them will be free and they will also let you access non-public domain books too, even the most recent titles.
For me, it's an everyday little miracle that publishers have not yet managed to convince lawmakers public libraries should be made illegal... because a lot of those publishers only want us to buy their books, much more than they want us to read them.
Public libraries are one of the most undervalued resource in many countries. One day, they will be gone, and a majority of us will not even care. Sad.
Whenever I get into discussion about piracy libraries gets brought up. Libraries are just pirates. One person buys a book and shares it with others for free. Same shit as piracy.
With the books is the same as with digital content. You are not buying the paper, you are buying the content. Except if you buy a book online you are for some reason not allowed to share it.
And yes I support piracy.
They make very nicely formated ebooks for our enjoyment.
Defiantly better than the wall of text you'll get from the .txt version or a lazily converted ebub.
If all of those links (also the two French ones I just mentioned) are 100% legit, unlike brick and mortar public libraries they offer little in guise of advice. If you have never tried talking with a librarian to get tailored reading suggestions, give it a shot. You may be surprised how useful they are. Also, they very rarely bite... only after they have been transformed into a vampire, or a werewolf.
(nope, I am no librarian but, yep, I may bite... in certain situations I won't publicly disclose :p)
I haven't done it myself, but I plan to watch a bunch of pre-Hays Code movies from the late 20s and early 30s. Many of these movies are in the public domain and more are entering it for the next few years.
Pre code movies are amazing. My mom watches a ton of them on YouTube, and I'll watch a lot of the time, too. They're genuinely hilarious to watch a lot of the time, because they showcase just how much hasn't changed. You feel like, because of media, we practically invented a lot of stuff in the last generation or two, only to watch Mae west talk about mirrors on her ceiling or Marlene Dietrich dress in dress.
I can't speak to public domain or not but it is available for download. If Wikipedia had a problem with it being downloaded, I'm sure they would be asking Google to remove the Kiwix app from Google Play.