Territory Weak Battery and Flickering Lights

Sounds like a plausible cause. Have you checked the battery voltage with a multimeter, both when the engine is off and while it's running? Are there any error codes being thrown by the car's computer?

I did check the voltage; it dips quite low during startup, and there are no stored error codes, which is puzzling. Could a failing battery sensor cause such a significant voltage drop without triggering any fault codes?

Yes, a faulty battery sensor can definitely cause those symptoms, even without throwing codes. It could be misreporting the battery's state of charge, leading to inadequate charging. Given your symptoms and the lack of error codes, replacing the sensor is a reasonable next step, or you can bring the car to a workshop for a diagnosis. Considering the 315€ repair price, they might offer a better price and pinpoint the issue.

Thanks. I took it to a workshop and, as suspected, the battery sensor was defective. Replacing it resolved all the issues; voltage is now stable, and the lights are no longer flickering.