[Substratum] Mono/Art Theme works with Google stock and custom AOSP based 8.1/9.0/10.0 ROMs. LineageOS aren’t fully supported. OxygenOS isn’t supported. Doesn’t work on Samsung devices running stock firmware. You need a substratum app from the Play Store to apply the theme. You need to be rooted
IMPORTANT! When you open the theme in the substratum app you’ll see the drop-down menu on top of the overlays. You need to choose one depending on your ROM Android version. There are also some overlays with different variants for specific Android versions.
HOW TO apply theme. Select all the overlays (if there are any options in overlay, read and choose wisely), press floating action, and choose Build & Update. Wait until the process is over and reboot. Open substratum again, select all the overlays you previously built, press the floating action button, and choose Enable this time. Enjoy the theme! For updating an overlay you need to Disable it first, Build & Update and finally Enable it. There’s no need for a reboot, except for Android System overlay.
After every update, I recommend a clean install (uninstall all the overlays from substratum Manager, reboot, and repeat the process like you did the first time). Also, after updating an app from the Play Store if it forces close, try first to uninstall overlay for that app and install it again. I recommend disabling auto-update the apps from the Play Store if you want a fully working theme.
Don’t report bugs if you’re using custom DPI