Lilygo T-Deck Firmware #
The T-Deck firmware can be downloaded from the usual location but it cannot enter bootloader mode as a USB drive like most other devices. Instead you must install CircuitPython using WebSerial, which only works in Chrome.
To install it, go to the CircuitPython download page in Chrome and click the Open Installer button. A dialog will appear. Select 'Upgrade CircuitPython 9.2.1 Bin Only', choose the device in the Chrome web-serial port selection dialog, and follow the prompts. This will download and reflash the device. Then turn the device on and off with the power switch and it should boot up with the usual CIRCUITPY drive.