The speaker at the FOSDEM conference in 2023 talked about the capabilities and features of Calibre, an open-source software for converting documents to different formats and integrating with different tools. The speaker highlighted the simplicity and efficiency of Calibre's API and how it can handle document conversion and other tasks that are currently being done in complex and inefficient ways. The speaker also mentioned collaborations with other projects such as Zotero and Language Tool, and discussed the importance of interoperability and improving document editing and formatting. They also mentioned upcoming features and events like the Hackfest and a collaboration with Cambridge College.