SUMMARY File: kolourpaint-22.08.3-1708-macos-clang-x86_64.dmg from https://binary-factory.kde.org/view/MacOS/job/Kolourpaint_Nightly_macos/ Feature request: add support for JPEG XL (.jxl) files.
sample file: https://w2w-images.sftcdn.net/image/upload/v1620662834/Ghacks/IMG_20200308_194050.jxl
Can you try these macOS builds? https://cdn.kde.org/ci-builds/graphics/kolourpaint/master/