The secret Utopia Battle Star of the seventh week of Season 9 can be found just outside of the Pressure Plant.
To actually make the battlestar appear, you must first complete a the full set of weekly challenges.
Once any five sets of them have been completed, this Secret Battle Star can be collected and the challenge “Find the Secret Battlestar in Loading Screen #7” will appear in the Utopia Challenges. It will reward you with one full battle pass tier.
Go to the volcano, Pressure Plant. Where the lava runs out of the volcano you have to go up the steel stairs. The exact location you see in the video.