All 5G iPhone 12 models support Dual SIM mode, which refers to the ability to switch between a SIM card and an eSIM operating on independent numbers and/or carriers.
However, an image of a training document from Apple’s Sales Web resources called “What you need to know about 5G on iPhone” and posted to Reddit suggests the iPhone 12 will not support 5G on either line when Dual SIM mode is active.
If we see Apple’s Dual SIM support page, there’s more information about that
