Doesn't seem like any of the OSS image processing servers support XL. A quick check over the docs of the major image CDN services and only Cloudinary has XL support (as expected, since their FUIF proposal was one of the foundations for XL along with Google's Pik). Chrome seem to have gone furthest in developing support for XL in Chrome, FF and Safari are way behind and there doesn't seem to be a clear signal from them that they'll continue working on it. From my perspective this really looks like Chrome isn't going to take the hit for being the only browser supporting an image format again, like it was for WEBP (which took years [and nearly a decade] to land in other browsers).