Custom overlays can no longer be installed on Android P. That means
no more rootless Substratum.
No more custom themes. It’s all gone.
For those of you who aren’t aware,
Android Oreo introduced Sony’s Overlay Manager Service (OMS) which can be controlled via an
ADB command. Using a clever trick, the developers behind the popular Substratum theme engine app were able to develop an add-on called Andromeda that allows Substratum to apply themes without needing root access. It was an incredible achievement as it was the first time that Google’s Android could be themed without needing a custom ROM or root to replace system files.