Update 1/8/19: The Paranoid Android team has released an Android Pie build for the Essential Phone as well. The team is also teasing an imminent release for the Xiaomi Mi Pad 4.
One of the most well-known custom ROMs around, Paranoid Android, is finally back. While its development has been on somewhat of a hiatus for a few months now following its Android Oreo release, Paranoid Android is back and based on Android Pie. It already boasts support for the Xiaomi POCO F1, Xiaomi Mi 8, Xiaomi Mi 6, Xiaomi Mi 5, and the Xiaomi Mi Mix 2S, with beta releases coming to the Essential Phone, OnePlus 6, OnePlus 6T, and the Moto G5 Plus in the near future.
Paranoid Android for the POCO F1 (beryllium)Paranoid Android for the Mi 5 (gemini)Paranoid Android for the Mi 6 (sagit)Paranoid Android for the Mi 8 (dipper)Paranoid Android for the Mi Mix 2S (polaris)
If you don't have any of those smartphones but want to give Paranoid Android a try, you can still give it a shot so long as you have a Qualcomm Snapdragon 835 smartphone running Android Pie. The Paranoid Android team has released a "QSSI," basically a Qualcomm CAF GSI that works on Project Treble-enabled devices with specific chipsets. QSSIs are released by chipset and not by architecture, so it won't run on any other chipset just yet. There is another caveat though, and that is that your smartphone must not use the A/B partition system. Therefore, devices like the OnePlus 5 and OnePlus 5T qualify.
Paranoid Android for the QSSI for Qualcomm Snapdragon 835 devices only
The existence of CAF is one of the many reasons why Android smartphones using Qualcomm chipsets are so popular with the development community. While the GPLv2 license requires that vendors release their kernel sources, that isn’t always enough for creating custom ROMs based on AOSP. This is not required for SoC vendors, but Qualcomm often provides the public part of their chipset specific code for HALs, framework branches, and more which is a great benefit for developers. Developers using this can then build for a platform without knowing how all the new chipset-specific features work, and without it, it can be a lot harder to build AOSP for a device.
The team has also said that they are in contact with the OpenKirin team to bring support to many Huawei and Honor devices. In addition, they are also in contact with XDA Recognised Developer phhusson, one of the lead developers working on Project Treble GSIs for the custom ROM community. As development continues, the team hopes to add even more features and improvements. The first release is in a beta state so currently only a few changes and optimizations were made on top of the stock Android CAF base.
Update: Essential Phone Release
A preliminary build for the Essential Phone has been released. Currently, night light doesn't work and custom kernels aren't supported.