Hi @Ankit Agarwal,
Thank you for reaching out to Microsoft Q&A forum!
Unfortunately, the English - Nigeria variant for embedded TTS is not currently available in Microsoft Azure. As of the current date, we do not have any information on the En- NG availability.
However, you can keep an eye on the Azure Speech services release notes for updates on What's new in Azure AI Speech and Embedded Speech page will be updated accordingly with more details.
I hope you understand. And, if you have any further query do let us know.
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