for online updates. Firmware updates for this specific model must be performed via the on the front panel. Step 1: Check Current Firmware Version
Because this model lacks a built-in Ethernet or Wi-Fi connection for direct updates, you must use a physical USB drive. Denon Avr-x520bt Firmware Download
AVR-X520BT - 5x 130W 4K Ultra HD A/V Receiver with Bluetooth | Denon for online updates