TD permits study and does not authorize employment. Whether a particular volunteer role falls outside employment depends on its specific facts, so a general yes or no is not available. The activity needs to be described in detail and reviewed before it begins.
The label is not the test
Organizations use volunteer, intern, fellow, and trainee loosely, and an internal title has no bearing on how an activity is characterized for immigration purposes. What matters is what the person does, for whom, on what schedule, and what the organization receives in return. Two placements sharing the same title can be assessed differently, which is why counsel needs the particulars.
TN credential requirements are profession-specific and come from the listing itself, not from general rules about degrees. TN admission requires citizenship of Canada or Mexico, a qualifying listed profession, prearranged professional employment, and temporary entry. TN status is available to eligible Canadian and Mexican citizens for prearranged professional work in a listed USMCA occupation, and the applicant must meet that profession's own qualification rule. Officers assess the work actually described, so a supervisory or hybrid title can move a qualified professional outside the category. The English wording should explain the work accurately, not turn general coordination into professional activity that the employer does not intend.