If the router is still working, then it is not bricked.
The main issue at the moment is that you’re unable to upgrade the firmware through the Admin Panel.
And the U-Boot is an alternative method for flashing firmware, so we recommend following the tutorial to try that approach.
You can also try downgrading to the stable v4.8 version first follow the steps below, and then upgrading to v4.9:
Please note that we do not recommend using backup files across different firmware versions, especially when it comes to minor version updates.