Something that we miss from the old Cyanogenmod Theme Engine is the variety of different status bar icons that we could choose from depending on the theme we installed. Sadly, fewer themes using Substratum include status bar icons, and if they do there tends to not be a great choice. However, thanks to XDA Senior Member svandasek, there is now a wide selection of status bar and WiFi icons to choose from! Svandasek put together a Substratum theme collection of some pretty great signal indicators which you should check out below! Note: We do not recommend using these on rootless Substratum on Android Oreo.
Substratum Signal & WiFi Icon Theme Pack