The placeholder text in the title input box here reads:
What's your Islam question? Be specific.
Is that sentence grammatically correct? Islam being a noun.
Yes. Nouns function as adjectives all the time in English - this actually distinguishes English from many Romance languages.
"I have a marriage problem."
"He's a football player."
or even "Try this new dessert - it's like a donut croissant."
In Spanish, you could not say "What's your Islam question?", but rather you would have to say "What's your question about Islam?". In Latin, the word "Islam" would be in what's called the Genitive case to mark it as functioning like an adjective.