Hi there, i have been moving a lot of my media into the JXL format and sadly seafile does not attempt to preview this. however if the browser has support it can work. i have already verified this by just lying to seafile and changing the filename to .png even tho its actually a jxl image. The image loads fine and without issue. I was also able to use this same method to get a JXL background image on login.
however naturally i would prefer to not need to change the extension of all my files locally for the sake of seafile. Similar to how there is an option for us to manually add extensions for txt files i would love the ability to add jxl or just have it officially added.