All external AVR microcontrollers with the UPDI interface can be programmed and debugged with the on-board debugger with Microchip Studio.
External SAM microcontrollers that have a Curiosity Nano Board can be programmed and debugged with the on-board debugger with Microchip Studio.
AVR64DD32 Curiosity Nano can program and debug external AVR64DD32 microcontrollers with MPLAB X IDE.