When using stm32duino with Platformio, STM32 macro is not defined. It's more reliable to use STM32_CORE_VERSION instead.
// #elif defined(STM32)
#elif defined(STM32_CORE_VERSION)
#define I2C_BUFFER_LENGTH_RX BUFFER_LENGTH // BUFFER_LENGTH is defined in Wire.h for STM32
#define I2C_BUFFER_LENGTH_TX BUFFER_LENGTH
When using stm32duino with Platformio,
STM32macro is not defined. It's more reliable to useSTM32_CORE_VERSIONinstead.