Siri - Change language without completing the setup
Select Setup “Hey Siri” Later. Then navigate to Settings > Siri &amp; Search, and toggle on Press Home for Siri. A pop up will appear in your system language. Select the top option to confirm you want Siri on. Then, you can customize Siri’s language and voice. You can now enable “Hey Siri” in the language that you would like.

You will be unable to change the language for Siri until the Press Home for Siri option is enabled.