The required layers are not specified in the Scarthgap branch

[tprrt]

The LAYERDEPENDS variable must be set in the layer.conf file to indicate that certain layers are required for using meta-atmel and to ensure compliance with OE/Yocto.

Additionally, please be careful: the Scarthgap branch contains an nginx_%.bbappend. This means that either meta-webserver should be included as a required layer, or you should utilize the dynamic layer feature.