https://cloudinary.com/documentation/image_optimization#auto...
Also, your claim is that you are "first to support", not "first to serve all our clients images as jxl without asking if thats ok"...
You dont need to use the f_jxl parameter. e.g. https://res.cloudinary.com/demo/image/upload/c_scale,w_500/f...
And can all be handled via srcset.