XA2 Revert to Android --> lock failing

I switched my Sailfish device from the XA2 Ultra to a 10 mark i and want to sell my XA2. I managed to install Android on it again using Xperifirm and newflasher. Now I want to lock the device again and thought this was possible using:

$ adb reboot bootloader
$ fastboot oem lock
or
$ fastboot oem lock *devicedeveloperunlockcode*

But both fastboot lock command result in:
FAILED (remote: 'unknown command') fastboot: error: Command failed

If I try to unlock, which it is already, I get a rather normal FAILED (remote: 'Device already unlocked').

Does anyone have a suggestion to what I’m doing wrong. I have no access to a Windows PC, so EMMA is not an option.

Haven’t tried but here’s some starters you might want to take a look at - considering that it’s even possible to relock the bootloader for the Sony devices:

https://source.android.com/devices/bootloader/locking_unlocking

According to developer.sony.com:

No. Once you have unlocked the bootloader, you will not be able to revert the device back to a locked or original state or restore the DRM security keys. You can however use the Flash tool for Xperia™ devices to flash a generic Sony ROM, although it will not receive automatic software upgrades.

Thanks, but the suggested fastboot commands don’t work. Guess I’m out of luck then. I know I had issues locking a Xperia X a couple of years ago but managed in the end. So this one is annoying :thinking:

For my Xperia X I had more luck, as I backuped the TA Partition according to:

I hope there will be a solution as I am not able to receive company e-mails as it is forbidden to install software on a rooted device.

I’m sorry I don’t know where is hidden that information but it’s not visible here:
https://developer.sony.com/develop/open-devices/get-started/unlock-bootloader/
As this is critical info it’s shame, that Sonny buried down that info instead of providing it on the unlocking page. May people probably wouldn’t continue to do that.