The KDE Frameworks are add-on libraries that can be used to build applications using Qt. Qt developers will be familiar with the API style of the Frameworks since they have been thoroughly documented and tested. KDE frameworks are developed following a proven KDE governance model with a predictable release schedule, transparent vendor-neutral contributor process, open governance, and flexible LGPL or MIT licenses. Cross-platform frameworks are available for Windows, Mac, Android, and Linux.
Daniel Novomesky is back again! He created the Plugin qt-jpegxl-image-plugin which allows you to read and write JXL images on Qt and KDE based applications. You will find an easy-to-follow installation guide on the linked Github page.