Information regarding general support for the STM32 can be found here: STM32 (uGOAL).

Specific information for small STM32 targets (G071RB, F103RB) can be found here: STM32F103RB / STM32G071RB (uGOAL).

There is a full features GOAL based platform for STM32F429ZI with some information here: STM32F429 (GOAL) .