We got a request from a customer for a board that makes connecting between a breadboard and Stemma QT or Qwiic components easy, and here's what we whipped up!
The Adafruit Qwiic / Stemma QT Breakout Board is pretty simple: on one end is a JST SH-compatible connector, that will let you plug-and-play to the Qwiic or Stemma QT universe. On the other side is four 0.1" spaced pads where you can solder header or wires as you wish. In between are two 10K pullup resistors from the two I2C SDA/SCL lines to the positive power pin, plus a green ON LED so you know when the power pin and ground are properly wired.
And that's it! Simple but effective. You can use it both with 'I2C controllers' like a Feather, Metro, QT Py, or with 'I2C devices' like sensors, OLEDs or GPIO expanders. Since the lines just pass through, you can use it with 3 or 5V power and logic. The LED and pull-up resistors can be deactivated by cutting some small traces on the back of the PCB, if they are not needed.