If you care about #signal , you should want #jpegxl support, especially as Apple now supports the image format ecosystem-wide. On Signal's iOS & macOS clients, users will become frustrated if they can view an image but can't send it to anyone using their favorite messaging platform while alternatives like #telegram support JXL. Please bring attention to this feature request:
https://community.signalusers.org/t/jpeg-xl-support/50331
There is an open GitHub issue: