No option to add esim

Mainland China phone models do NOT offer eSim options. If you need eSIM, return the phone for a refund or sell the phone.

If you had purchased from an authorized Apple dealer in Hong Kong, you might see eSIM options on the phone.

_support_apple_ wrote:

Thank you for the information. I bought it from authentic apple store in china mainland. No where it is written that the china models do not have esim.

From: About eSIM on iPhone - Apple Support

From the tech specs, dual nano-SIM. (No reference to eSIM):

And…

透過兩張 nano-SIM 卡使用雙 SIM 卡功能 - Apple 支援 (香港)

And…

如果你的 iPhone 13 mini、iPhone 12 mini、iPhone SE (第 2 和第 3 代) 或 iPhone XS 在香港或澳門購買，請了解如何透過 eSIM 使用雙 SIM 卡。

And…

iPhone 尚未在中國大陸提供 eSIM 功能。在香港和澳門，iPhone 13 mini、iPhone 12 mini、iPhone SE (第 2 和第 3 代) 和 iPhone XS 均提供 eSIM 功能。進一步了解如何在中國大陸、香港和澳門透過兩張 nano-SIM 卡來使用雙 SIM 卡。

You get an iPhone with eSIM.

The dual-SIM iPhone sold in China is dual nano SIM only. There is no eSIM.

The following omits iPhone 15, but the dual-SIM version is the same as iPhone 14:

Using Dual SIM with two nano-SIM cards - Apple Support

No where? You might want to check this Apple Support document for information about China:

Wireless carrier support and features for iPhone in Asia-Pacific - Apple Support