eSIM is a completely different SIM card system. It is not a physical SIM card. It is usually attached to the phone’s processor during manufacture and can interact with it like a physical SIM card. However, most phones do not support this particular eSIM technology.
Oppo Reno8 (China) phone is based on a dual SIM system. However, the phone does not provide the facility of eSIM. You need to connect through a physical SIM card. But you can communicate without a SIM card through the WiFi calling system.