it took about 3 days and bricking my phone 5 times to get it right, but I finally got Lineage OS on my Oneplus, hopefully you don't go have as much trouble as I did.

Windows binaries for fastboot and adb
https://forum.xda-developers.com/t/recovery-3-4-0-10-u-guacamole-official-unofficial-twrp-recovery-for-oneplus-7-pro.3931322/

Nebrassy TWRP (the one I used)

https://forum.xda-developers.com/t/recovery-11-unofficial-teamwin-recovery-project.4289455/

copy partitions (If system doesn't show up to wipe)
https://androidfilehost.com/?fid=2188818919693768129

lineage OS download
https://download.lineageos.org/guacamole


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