I would like to ask this question "What was the religion of Samuel Insull?" (he was a very important businessman who greatly contributed to creating an integrated electrical infrastructure in the United States) - is it OK to ask such questions on History SE?
It's not OK when the answer is a few basic searches away. In such cases, the question would likely get closed as 'too basic'.
It's fine if some cursory googling yields no answer. In this case you ideally want to highlight:
What you've found so far, e.g. "His/Her wikipedia page is silent on the topic".
Why you suspect that person to not have the dominant religion of their area or identity group at that time.