The United Arab Emirates is not a party to the Hague Service Convention and has no service treaty with the United States, so there is no Central Authority route. The formal alternative is Letters Rogatory through diplomatic channels, which typically take a year or more. In practice, most U.S. litigants serve UAE defendants through a local agent or by a method the court orders under FRCP Rule 4(f)(3).
The UAE is also two legal systems in one. The onshore courts of each emirate apply civil law and work in Arabic, while the Dubai International Financial Centre (DIFC) and Abu Dhabi Global Market (ADGM) have their own English-language common-law courts. Where the defendant is, and where any judgment might need to be enforced, shapes the best approach.