PlatformIO has no native support for debugging with an Atmel ICE (only uploading) – simavr (simulation) and avr-stub (gdb stub on the target microcontroller communicating over UART) are the built-in ones for now.
You may still be able to use AVaRICE as shown in Atmega32 debugging with avarice and avr-gdb - #2 by mate910327 to get a gdbserver and debugging up and running within PlatformIO.