Chrome or Edge on a desktop. Same images the device installs over Wi-Fi
after SETUP → WiFi → Join.
Web Serial is unavailable. Open this page in
Google Chrome or Microsoft Edge
on a desktop PC (not iOS).
P4 uses the USB TO UART port (QinHeng 1a86:55d3),
not USB OTG. A blank board still needs a first PlatformIO flash
(bootloader + partitions). This page writes the app image.