Add Bluetooth to your knob

The knob talks to Bluetooth headsets and speakers through a second chip beside its main one. When its configuration page says that chip does not answer — or shows no Bluetooth headset or speaker at all — the chip has no firmware on it yet. Put it on from here, over the knob's USB-C cable: a few minutes, once. From then on the knob keeps it up to date by itself.

What it takes

Chrome or Edge on a desktop or laptop — Windows, macOS, Linux or ChromeOS. Other browsers, and phones, have no Web Serial to reach the knob with.
A USB-C data cable. The knob's USB-C reaches its main chip one way round and its second chip the other: the page asks you to turn the plug over. At the end you unplug it and switch the knob off and on again.
A knob made by RF.Guru: the page checks it by its MAC address first.
On Windows, the second chip's USB serial port (a CH340) may need its driver: from its maker, WCH (CH341SER), or from Windows Update.
On Linux, your user in the serial ports' group — dialout on Debian, Ubuntu and Fedora, uucp on Arch — then log out and in again.

What it does

Fetches the second chip's firmware from GitHub, every file checked against its sha256.
Reads the knob's MAC address — the knob restarts — and checks that RF.Guru made it. Nothing on the knob changes: its firmwares, WiFi and settings stay as they are.
Writes only an ESP32-U4WDH at revision 3 or later, the knob's second chip: anything else on a USB serial port is left alone. A chip with something else on it is erased first; one set up before keeps its headsets' and speakers' pairings.
Restarts the chip, and checks that it runs the firmware written.

A second chip that will not take its firmware here, or a page that stops part way? Open the Log above and report a problem, with the log in it.