In Genshin Impact, if you're considering using Aether in Natlan, the element you choose would depend on the context of your team composition. Natlan is expected to be associated with the Pyro element, given its themes and setting. Therefore, using Aether as a Pyro character would allow you to synergize with other Pyro characters and elemental reactions.
However, it ultimately depends on the characters you want to pair Aether with and your specific team strategy. Keep an eye out for upcoming updates, as additional characters and mechanics may provide more options and strategies for utilizing Aether in Natlan or any other region.