I am adding some collectables to my Movie collection which clearly aren’t movies. When searching for images online nowadays WEBP images are used quite often. So I downloaded a couple of images which are WEBP instead of JPG.
When I upload this image as cover in the application it works fine:
Indeed, desktop doesn’t support Webp and we also do not convert it during sync. I recommend to stop using Webp if you want to keep working with the desktop version.