E has several different meanings or uses, depending on context. In the case of Aloha e Kaleo, "e" acts as an object marker. Youʻre saying Aloha (to) Kaleo. When starting a sentence, it often indicates the start of a command, like: E Kaleo, e pani i ke kula (Hey Kaleo, close the door!)
ABOUT THE LACK OF AUDIO EXAMPLES: No, its neither a lag on your phone, nor the app Its just that the Hawaiian language is in fact indangered, thus not many people are fluent speakers. That is why the Duolingo app has few sound examples; because they havent veen developed due to the lack if "staff".