Unlocked units XDA thread: https://forum.xda-developers.com/t/op8-oos-21aa-ba-da-unbrick-tool-to-restore-your-device-to-oxygenos.4085877/

T-Mobile units XDA thread: https://forum.xda-developers.com/t/op8-oos-tmo-55cb-unbrick-tool-to-restore-your-device-to-oxygenos.4093043/

Verizon units XDA thread: https://forum.xda-developers.com/t/op8-oos-vzw-67cd-unbrick-tool-to-restore-your-device-to-oxygenos.4191723/

Visible units XDA thread: https://forum.xda-developers.com/t/op8-oos-vis-68ce-unbrick-tool-to-restore-your-device-to-oxygenos.4203017/

Specific notes:

When using Android Q MSM tools, backup your /persist as a precaution to prevent loss of fingerprint sensors. You need to root your device and use dd if=/dev/block/bootdevice/by-name/persist of=/sdcard/persist.img should you wish to do so. If you failed to backup this partition which is unique per device, you may want to follow instructions at https://forum.xda-developers.com/t/guide-fix-persist-img-loss-of-finger-print-sensor.4126455/ to recover your fingerprint sensor.

Using Verizon MSM tool will change warranty date in About Phone -> Status to "None". This is not something anyone can do anything for, as of writing on January 2021.