@oscarjiminy @MarkHoltom @dmetzgar I'd say it doesn't really matter that much. If you just want to plainly say that you were born in Frankfurt or live in Frankfurt, then you'd typically leave out the article (“Ich bin Frankfurter”). For example, there was an anti-racism campaign called “Ich bin Münchner – ich bin Muslim” in 2018 whose intention was to emphasise that Muslims are regular Munich citizens. When you do use the article, then that can either mean the exact same or have a slightly figurative meaning. For example, there's a Wise Guys song titled “Weil ich ein Kölner bin” (Because I'm a Cologner) which humorously references certain stereotypes associated with Cologne citizens. Though, I'd also say many people would probably casually prefer “I'm from…” to “I'm a…”.