You don’t need a flight controller running beta flight to use the FETtec Configurator. @TeeZee shared an informative video of how to make a simple half-duplex wiring that allows you to use the configurator with a simple usb/serial adapter. It works great - and is super simple.
@TeeZee illustrated the wiring using a breadboard - but I made a simple wiring setup with the required diode. Since I’m not using One-Wire - its all part of the ESC connection to the copter - I used a PH connector so you could simply plug in the connection bit with the diode. If you’re using One-Wire, you’d have to disconnect the JST-SH from the ESC, and replace it with one with the necessary wiring to use the USB-serial adapter.
And it works at all the baud rates I tried. I settled on 115200.
It does appear like the published information about all this is either inaccurate, incomplete, or out of date.
I’m guessing that FETtec doesn’t anticipate many ArduPilot users. If it did, they would have included wiring instructions for One-Wire - where the four motor leads are connected together for UART. (the TX, as I recall - I can’t remember off hand)
Reference: FETTec OneWire ESC - getting the FETTec Configurator to work