please check also if there is a way to serve the covers as next-gen format WebP in the app at yootheme.
right now lighthouse is marking all images from the "EB yootheme app" as to slow:
https://www.screencast.com/t/C2ONMKLov2
right now lighthouse is marking all images from the "EB yootheme app" as to slow:
https://www.screencast.com/t/C2ONMKLov2