Installed Android 14 (U) ‘guacamoleb’ on the Oneplus 7 (GM1903) yesterday. The documentation reads to first be on the latest Android and then to run the OEM unlock. The issue is however that then the Android 12 OxygenOS you run on, gives this issue, due to a bug introduced by Oneplus:
fastboot oem unlock
FAILED (remote: 'Device cannot be unlocked for technical reason.')
fastboot: error: Command failed
The only solution is to rollback to Android 11, using their rollback tool:
https://community.oneplus.com/thread/1181216999612088323
The next issue you run into is that Oneplus changed their download links to another place, so you run into a:
Error code: 404 Not Found
To solve this, You need to add “https://s3.amazonaws.com/oxygenos.oneplus.net/” before the name of the file you want to download and the downloading will start. Or use a CURL.
sources:
https://xdaforums.com/t/downgrade-op-7-pro-to-android-11-to-unlock-oem.4554561/
https://xdaforums.com/t/download-oxygenos-rollback-package.4712819/
After applying the rollback as follows:
* Download the latest ROM rollback zip package from the specified server.
* Copy the ROM rollback package to the phone storage and rename the package according to different regions, you may refer to the note below.
* Go to Settings -> About device -> Version -> Click Build number 7 times and enter the password, now you are in the developer mode.
* Go back to Settings -> About device -> Up to date -> Click the top right button -> Local install -> Click on the corresponding rollback package -> Extract -> Upgrade -> System upgrade completed to 100%.
* After the rollback is complete, click Restart.
* Rollback successful.
You can proceed with the fastboot OEM unlock on the stock Android 11 that will popup after the reboot. No need to upgrade to stock Android 12 afterwards, you can just install e-2.9-a14-xxxxxxxxx-community-gucamoleb.zip. Wish I knew this before, took me hours to figure out.
https://doc.e.foundation/devices/guacamoleb/community
Happy flashing!