Bonus points if they are indie sites and no crude responses please.
JSTOR: It has a good selection of open access books[https://about.jstor.org/oa-and-free/] (supplement with individual publishers[you can find many from DOABOOKS, https://blogs.openbookpublishers.com/covid19-information-and..., https://www.oapen.org/researchers/13516596-funder-compliant-..., or https://www.oaspa.org/] & doabooks[https://www.doabooks.org/]). I like reading that sort of thing. I've been enjoying Stand Out of Our Light[https://www.cambridge.org/core/books/stand-out-of-our-light/...] by Cambridge University Press, which is legitimately engaging and not written very academically.
Wikipedia: Duh. Favorite page is the Unusual Articles[https://en.wikipedia.org/wiki/Wikipedia:Unusual_articles] one.
Internet Archive: Amazing. Especially the books. Supplement with the Online Books Page list of archives.[https://digital.library.upenn.edu/books/, click on 'Archives and Indexes']
Find Your News[https://findyournews.org/]: Directory-ish of nonprofit news outlets. Missing, last I checked, many of the ones in Hung-Su's list of slow news outlets[https://hung.su/slow-news-movement/], so I tend to use them together when I'm in a bingeing-on-nonprofit-news mood.
NEH Humanities Magazine: The US National Endowment for the Humanities has a magazine[https://www.neh.gov/humanities] that covers a lot of historical subjects, and it's free (online at least). Similar ones are available from the Library of Congress and National Archives, but I don't read those nearly as often.
I also like pluralistic [https://pluralistic.net/], Kottke [https://kottke.org/], The Marginalian [https://www.themarginalian.org/], Freerice (take quizzes, feed kids. Worst thing that happens, you learn)[https://freerice.com/] and the wonderful Marginalia search engine: https://www.marginalia.nu/.