Looking at the supported SAMD boards in the repo at
https://github.com/micropython/micropython/tree/master/ports/samd/boards. Though there's a SAMD21x18a linker script (the CPX uses a SAMD21g18a MCU) which is also what the Feather M0 Express uses, and that's supported. So it probably woudln't take much. You could probably crib code from CircuitPython's CPX support.
Dave