LineageOS has rolled out support for the 2016 Google Pixel and Google Pixel XL in their latest firmware build of Android Oreo 8.1. In LineageOS terms, that build 15.1. The addition of the two Google phones adds to an ever increasing number of devices that the independent Android development group, which rose from the ashes of CyanogenMod, supports.
Like other phones, in order to use LineageOS on your Pixel or Pixel XL, you will need to have the bootloader unlocked and be comfortable with manually installing a software build. It isn’t an overly difficult process but if you aren’t familiar with the process or comfortable with it, its best to stay away.