What is GwenView?
The KDE Applications bundle contains Gwenview, an image viewer for Unix-like systems (including Linux). With Gwenview, you can browse and display various collections of images quickly and easily. Simple image manipulations are supported, including rotating, mirroring, flipping, and resizing. Additionally, it supports basic file management actions such as copy, move, and delete. The viewer works both as a standalone application and as a Konqueror web browser extension. KIPI plugins allow it to be extended further.
GwenView JXL support
GwenView has added JPEG XL support about a year ago. Earlier in 2021, a quality chooser was implemented as well. This means that you can easily use JPEG XL as you are used to by any other format.