Just to try to summarize the comments on the question:
This depends very much on the specific focus of the question.
If the question is seeking recommendations on which financial institutions will be least likely to be bothered by the fact that the person is an undocumented immigrant, that would very likely be considered off topic as a product recommendation ("which bank should I use?").
If the question is seeking facts about a process, then the fact that the person that would be going through that process is an undocumented immigrant would likely be, at most, peripheral. For example, asking how a person in a given situation in the United States could establish their identity to a financial institution sufficiently to be allowed to open an account, is likely to be on topic.