Apple Plans to Enable 5G in Dual SIM Mode With Software Update Later This Year

iPhone XS models and newer feature both a physical SIM slot and a digital eSIM, allowing for a feature known as dual SIM, dual standby. This means you can have two lines of service on one iPhone, which is useful for purchasing data-only plans while traveling abroad or having personal and business lines on a single iPhone.
5G will not be available in Dual SIM mode on the iPhone 12 and iPhone 12 Pro at launch, however, according to an internal training document for Apple employees shared on Reddit