Oneplus has released the update 5.1.4 which is making your device ready for "Project Treble".
LineageOS can only be installed on phones being prepared for "Project Treble".
### Terminology
-**firmware** : Controls the modem and baseband of a device
### What you need to know
- If you are installing from versions lower than 5.1.4 then you need to update your **firmware** to
version 5.1.4 first which will apply the required changes for "Project Treble".
- To update your firmware:
- Download the 5.1.4 firmware for [cheeseburger](https://sourceforge.net/projects/cheeseburgerdumplings/files/15.1/cheeseburger/firmware/) / [dumpling](https://sourceforge.net/projects/cheeseburgerdumplings/files/15.1/dumpling/firmware/).
- Copy the downloaded firmware `.zip` to your phone
- Boot into TWRP recovery and flash the downloaded firmware `.zip`
- Reboot
- Follow the install instructions
### Firmware packages
- Firmwares for LineageOS 15.1: [cheeseburger](https://sourceforge.net/projects/cheeseburgerdumplings/files/15.1/cheeseburger/firmware/) / [dumpling](https://sourceforge.net/projects/cheeseburgerdumplings/files/15.1/dumpling/firmware/)
- Firmwares for LineageOS 16.0: [cheeseburger](https://sourceforge.net/projects/cheeseburgerdumplings/files/16.0/cheeseburger/firmware/) / [dumpling](https://sourceforge.net/projects/cheeseburgerdumplings/files/16.0/dumpling/firmware/)