@bettina@mastodon.nu @FrankBlack78@social.tchncs.de @itsfoss@mastodon.social USB applies to copying non-DRM ebooks in azw3 format to physical kindles. Only K1, K2 & DX family don't use azw3, which is closest to epub. Send to Kindle: Amazon converts to KFX, deletes fonts & resizes/reduces quality on images. There are file size limits too (larger on Web interface than email) and it uses Internet twice. Amazon get a copy. Using Calibre (free on Mac, Linux, Windows) to convert epub (or other reflowable formats) to azw3 is closest to epub.