AltSoftSerial pins on Adafruit Feather M0

I'm moving a project to a Adafruit Feather M0 Logger and was hoping to continue using AltSoftSerial to interface with GPS.

I'm trying to find out which pins AltSoftSerial would use with this model. It is not listed in the boards.h file.

Is AltSoftSerial compatible with the ARM M0+ ?
These are the supported processors: AltSoftSerial/AltSoftSerial_Boards.h at master · PaulStoffregen/AltSoftSerial · GitHub
Is that the "boards.h" you are referring to ?

The ARM M0+ has 6 SERCOM devices. Why do you want to use a software implementation for serial communications ?

That makes sense. I didn't realize the additional SERCOM capabilities of the chip.