When I reboot into the bootloader after step 1, I get a bunch of empty folders with scrambled numbers and letters in the sdcard directory.
I did manage to fix this by the following:
1. adb push (copy partitions, lineage, gapps zips in terminal)
2. adb reboot bootloader
3. fastboot boot twrp.img
4. install copy partitions zip in TWRP
5. install lineage in TWRP
6. reboot bootloader from TWRP
7. format data in TWRP
8. reboot bootloader in TWRP
9. adb sideload from TWRP
10. adb sideload gapps.zip (terminal)
11. reboot bootloader in TWRP
12. fastboot -w in terminal
13. start from bootloader