adb reboot bootloader && while fastboot flashing unlock; do echo Retrying in 5s; sleep 5s; done;
You have to see somtheing like this
OKAY [ 0.020s]
Finished. Total time: 0.020s
Then choose “Unlock bootloader using “Volume Down” -> “Power on” button. Phone will restart and boot to fastboot mode again. After this the status of the bootloader will be changed: “Device state: unlocked”
fastboot flash boot boot.img
adb sideload lineage-19.1-20230425-nightly-blueline-signed.zip
Total xfer: 1.00x