aospUI BlueGray is the first and most strongly AOSP UI inspired dark theme, it's "the old" DarkStockTheme.
If you like dark themes and you love Google's Android design, this merges the two ideas together.
The theme installs through an app that this app will link you to, IT REQUIRES ROOT (except on OMS rootless, Oreo and on Samsung Touchwiz Nougat/Oreo system, where you will have to buy an add-on made by Substratum developers).
The theme supports the following systems:
-AOSP/Custom/Google ROMs from Nougat, up to Pie;
-OxygenOS Nougat and Oreo;
-Samsung Nougat and Oreo stock system (including S series, Note series, A series and J series).
On Samsung Nougat notifications can't be made dark.
Other manufacturers' ROMs aren't guaranteed to be compatible (the more different they are from AOSP or Google ROMs UI, the more they're likely to not be compatible.
In case you end in bootloop flash the rescue zip that you find in /sdcard/Substratum/ (the substratumLegacy one if your ROM is RRO. Only most custom ROMs have OMS, the rest has RRO) and ask for refund, also by e-mail if you need.
Themed elements list (70+ apps): http://txt.do/dlvhx
Thank you all for supporting me. :)