One of the primary reasons users love Android is that they can customize their smartphone, from the launcher, to the look of the icons, to a full change of theme. This type of customization is reaching a new level with Android 8.0 Oreo, since now, you don't even have to root the device!
At the moment, if you want to customize your phone using themes, then you either have to root and use custom ROM permissions, or have a phone that came with the function built-in to the manufacturer's UI. But now, Substratum developers have announced on the XDA Developers forum that they have a way to use Android Oreo (without root) to apply themes.
Overlay Manager Service (OMS) evolved out of Sony's theme engine, called RRO (Runtime Resource Overlay), which has been integrated within Android since 6.0 Marshmallow. It's thanks to OMS that Substratum developers can make themes happen on Oreo without root.
There are two drawbacks to keep in mind. First, you'll need to plug your phone into your PC, install a PC application, and get Substratum for your phone from the Play Store. Second, when you turn your phone off and on again, you'll lose changes you've made, which doesn't normally happen with soft reboots or restarts.
These two little drawbacks may keep some from trying out themes without root. Nevertheless, it's an interesting development of the Android customization of the moment, and in conjunction with Project Treble, it should lessen the workload for OEMs, allowing them to push updates even faster with the theme aspect out of the way.
Will you give it a try? Let us know how it goes in the comments below.