"How do I determine if a trust is resident or non-resident for Mass fiduciary return?"
If you look at page 4 of the instructions (link below), it appears as if the trust satisfied one of the requirements for MA residency (you are an MA resident trustee), but none of the other requirements appear to be applicable.
See page 4: https://www.mass.gov/files/documents/2019/01/25/dor-2018-fido-form-2-inst.pdf
