There is a core for the Arduino IDE supporting the STM32MP1 at https://github.com/stm32duino/Arduino_Core_STM32.
The Arduino_Core_STM32 seems to be maintained now by ST.
There is a core for the Arduino IDE supporting the STM32MP1 at https://github.com/stm32duino/Arduino_Core_STM32.
The Arduino_Core_STM32 seems to be maintained now by ST.