@afewbugs I like Kobo as an e-reader. I just bought a color so I can read comics on it as well.
All the DRM stripping I've done has been through Calibre and the (DeDRM) plugin. Any books I couldn't remove the DRM from, I acquired through other means. As for "from any source" Calibre can also convert most things to epub and mobi.
Kobo has an ebook store. Ebooks.com has a UK shop. Some authors will have a way to purchase ebooks from their websites.
Thalia.de sells English language ebooks as well.
I've started self-hosting my ebooks and audiobooks (because there got to be so many) so feel free to ping me!
@afewbugs It's so frustrating when the terms suddenly change, which is why I've stripped DRM and we now self-host all our media (movies, TV shows, music, ebooks, audiobooks, etc.).
The only problem is with the rise of AI datacenters, the price of hard drives has increased drastically so we're keeping an eye on prices because we're starting to run out of space. (And we need to move things into a new case with available space. When we remove the oil boiler and the fuel tank to put in the heat pump, we might set up a wall mounted server in the basement.)