SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world.
And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download two short videos (registration required) highlighting:

System Workbench for STM32

how to convert stm32f103 usb mouse example to keyboard?

change the usb “HID” descriptor from mouse to keyboard
you may have also to review the usb confg (more than 4 byte per packet)

i did that for Mousse to gaempad and it wasvery easy
But for kayboard it may not be so straigt forward or simple