The original Pixel and Pixel XL smartphones launched with Android 7.1 in October of 2016. At the time, they were some of the only Android phones with three years of guaranteed software updates, and ended their lives running Android 10. But the old Pixels just got a new lease on life, thanks to the LineageOS team.
You can now run LineageOS 18.1 on the original Pixel or Pixel XL. This operating system is based on Android 11 and introduces some new features to the old Pixel smartphones, including the Android 11 notification panel, new emoji, and an updated autofill system for the keyboard.
Installing the OS on an old Pixel phone is a fairly easy task—it’s more time-consuming than anything. You just unlock your Pixel’s bootloader, install a custom recovery tool (like the TWRP recovery environment), and load the LineageOS 18.1 ROM.
The LineageOS 18.1 installation works quite well on the original Pixel, though of course, it isn’t totally bug-free. Also, it doesn’t come with Google’s suite of custom apps. If you want a more authentic Android experience, you’ll need to flash a GApps package.
Bear in mind that LineageOS works on a wide range of devices. You can see the full list of supported phones and tablets at the LineageOS Wiki.
At the time of writing, the LineageOS team is working diligently on its LineageOS 19 release. This upcoming operating system is based on Android 12 and should bring exclusive features like Material You theming to older phones.
Source: XDA Developers