When you open the theme in the substrate application, the drop-down menu appears above the layers. You must choose one based on your Android version of the ROM. There are also overlays with different variants for a specific version of Android.
AOSP applications such as Clock, Messaging, Gallery, Contacts, and Dialer may or may not work because each custom ROM has its own variant to these applications.
Supported Android
{7.0 and UP}
Supported Android Version:-
Nougat (7.0 – 7.1.1) – Oreo (8.0-8.1)
Download edge substratum 5.7 Patched APK For Android