https://www.libreture.com/bookshops/ has a list of stores (and for Norwegian books there is https://ebok.no/ ), but I have found no way to search "globally" (across sites like that) for DRM-free ebooks.

https://news.ycombinator.com/item?id=32442549 has some more tips.

Oh and https://bookshop.org/beta-search now actually lets you check "DRM-free" when you search, which is a very good step in the right direction!

I have a dream of https://news.ycombinator.com/user?id=marginalia_nu taking up the mantle. Though I think anyone could make something that's better than what we have now, which is nothing.

Not for buying, but for free: https://standardebooks.org

The best solution I have found is to buy a DRM book, then download the DRM-free version from libgen. That may not be what you're looking for but it keeps me in Calibre.

I've purchased a lot of mine from Kobo. There's also Standard Ebooks if you want free, high-quality reproductions of public domain works.

Note that with Kobo you need to check. I bought one there once thinking it was DRM-free, it was not.

One can also remove DRM from books one purchased with Calibre+DeDRM plugin.[0],[1],[2]

[0]: https://www.reddit.com/r/Calibre/comments/1c2ryfz/2024_guide...

[1]: https://www.mobileread.com/forums/showthread.php?t=361503

[2]: https://forum.linuxconfig.org/t/calibre-and-dedrm-problems/8...

For books in German, Beam is a very good choice: https://www.beam-shop.de/