ATmega48PB/88PB/168PB is supported in IAR Embedded Workbench® for Atmel AVR® - a commercial C/C++ compiler that is available for 8-bit AVR. Users of IAR must ensure their current installed version supports ATmega48PB/88PB/168PB.

There is a 30-day evaluation version as well as a 4 KB code size limited kick-start version available from their website: https://www.iar.com/iar-embedded-workbench/partners/atmel/