DFRobot has their own plug-n-play system as well, called Gravity. It uses 3-pin JST PH connectors for digital/analog and 4-pin JST PH for I2C and UART. However, Gravity is not electrically compatible with STEMMA: the order of the signal and power wires is different, including reversed power polarity and reversed I2C signal wires.  The JST PH plugs are physically the same as used for STEMMA, but you may damage your boards by intermixing STEMMA and Gravity, and they will not work.