While it is possible to use alternative power supplies with the Raspberry Pi 4, it is highly recommended to use the official Raspberry Pi 4 5V 3A Type-C USB Power Supply or a power supply with similar specifications. Using a power supply with insufficient current rating or unstable voltage may cause the Raspberry Pi 4 to malfunction, experience performance issues, or even get damaged. It's important to select a power supply that meets the recommended specifications to ensure the reliable and safe operation of the Raspberry Pi 4.