Apparently you have made a decision to automatically convert all images to WEBP format. Even for Shopify Plus customers, I guess we have no option to disable it? That is a huge limitation compared to other e-commerce solutions, that we can not control image format ourselves.
Besides loosing control, our issue now is that our e-com managers often download images from one instance and uploads into another. But since you do not support WEBP format when uploading (?!), we can no longer share images between instances.
Please, tell mere there is a way to disable this feature?
In the interim, please see if your team can use a browser that does not support webp (such as Safari with version less than v14) while downloading images. Shopify will serve jpeg image if the browser does not support webp.
See a list of browser versions supporting webp at https://caniuse.com/webp
Hope this helps in the interim while we get a upload support for webp.
This is the workaround we used in our Shopify implementation, when we came across the need to download webp images as jpeg. It may not work for you based on what you have noted. Yout could try searching for "saving webp images as jpeg" on the web and see if any suggestions work for you in the interim.
Per this link, even though you upload jpeg images, Shopify will serve them as webp if the browser supports it.
I hope someone from Shopify can clarify this further.