Download the unofficial LineageOS 16 build from the following page
Unzip the file with
Write to SD Card
Either use the instructions on the following link to write it to the SD card
Or use DD
WARNING! Make sure “/dev/mmcblk0” is the correct SD Card. Refer to here if you need to locate the path for the SD Card.
sudo dd if=~/Downloads/lineage-16.0-20200207-UNOFFICIAL-KonstaKANG-rpi3.img of=/dev/mmcblk0 bs=1M status=progress
Plug you SD Card into your Pi and boot it up.