Is it permissible to work with a company like Uber, under its system in which there is no actual contract between the driver and the company, and in which the company sets the price of the ride and deducts a 25% commission, bears no losses incurred by the driver, and considers drivers partners in name only?

We have not come across documented information regarding Uber's treatment of drivers. However, it appears that the driver is considered a sub-contracted employee of Uber. The agreement between them includes the driver receiving 75% of the trip cost, and the company compensating the driver for waiting hours, provided he is connected to the internet and using the company's application. This makes the contract a lease (ijarah) contract, not a brokerage (samsarah) contract. The company's determination of the delivery price does no harm if it is known to the driver before starting the trip. However, if the driver begins the trip without knowing the price, this constitutes ignorance (jahalah) which invalidates the contract. There is no objection to the company canceling the driver's subscription without warning after the completion of a delivery, as each delivery is an independent job and an independent lease unit.