Go Into bootloader

adb reboot bootloader

Unlock bootloader

fastboot flashing unlock or fastboot oem unlock
Restart and go back into bootloader

Flash recovery image

Download TWRP, fastboot flash recovery ~/Downloads/twrp-3.2.3-0-flo.img
Restart and go into recovery (hardware keys power btn, volume down to go into bootloader, then select recovery. Alternatively fastboot boot twrp.img if OS replaces recovery on boot)

ROM install

Download custom ROM and GApps
adb push FILE /sdcard/ both rom and gapps zip files
Install first the ROM, then install gapps

Install SuperSu using TWRP and Lucky Patcher app

(Optional) Apply Android Go optimizations to any ROM

Oneplus One firmware updates

To unlock bootloader, install custom recovery, and install lineageos itself https://wiki.lineageos.org/devices/bacon/install

Download GApps https://github.com/opengapps/opengapps/wiki/Package-Comparison

Push OS and GApps zip files to device adb push FILE /sdcard/

Install LineageOS, go back, reboot -> Recovery, then install GApps

check if we have root using adb root and adb shell, if don't have need to install supersu or lineagesu

nightly builds

https://download.lineageos.org/bacon

Nexus 7 (2013)

AICP Rom Extending /system partition to install Gapps