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

Can't create Ac6 Debug Configuration to CubeMX project


Do you use the latest version of System Workbench ? Please verify it by selecting : Help > Check for updates...

Then delete every debug configuration previously created and associated to your project : Project properties > Run/Debug Settings, select all, then delete them.

Finally, try to recreate the Debug Configuration :
Right click on the project, then choose Debug As > Ac6 STM32 C/C++ Application. It should automatically create the debug configuration and launch de debug.
System Workbench should ask you to create a custom board as Vetch said.

Hope it works,