Calibre 7.21 introduces a tool for creating an audio overlay in EPUB files, enabling users to listen to the text with sentence tracking using the read aloud functionality. It also improves dark mode contrast and adds new context menu actions.
https://alternativeto.net/news/2024/11/calibre-7-21-introduces-a-new-audio-overlay-feature-with-sentence-tracking-for-epub-files/