Until now I have always programmed my ATMega2560 Standalone with Arduino Uno (I removed the 328P chip).
Now the matter is getting serious and I bought a Pololu USB AVR Programmer v2.1, with Arduino IDE it is really fast at loading skatches.
I would also like to use it with PIO.
My current platform.ini configuration:
[env:atmega2560] platform = atmelavr board = ATmega2560 framework = arduino lib_deps = rocketscream/Low-Power@^1.81 xreef/EByte LoRa E220 library@^1.0.3 board_hardware.bod = disabled upload_speed = 9600 build_flags = -DFREQUENCY_868 monitor_speed = 9600 board_build.f_cpu = 8000000L board_hardware.oscillator = internal upload_port = COM8 monitor_port = COM8
On Arduino IDE I set the Programmer: STK500 as ISP (MegaCore) and I using COM7 programming port
And the parameters of the Pololu is