Samsung is now pushing a software update in the USA, which activates the eSIM for the devices. Not all devices are getting this update right now. This is coming late, because there are only two companies that were supported by the carriers for the eSIM- Apple and Google.
Samsung flagships do have eSIM – carriers didn’t support them.
Its true that many of the flagships have eSIM, but majority of the carriers in the country didn’t support them. However, things are changing. As of now, devices on T-Mobile are receiving this update. And as of now, the Galaxy Note 20 series is getting the activation update from T-Mobile. This essentially makes a path for the Dual-SIM phones in the country – one eSIM and other one being a physical or an eSIM.
As of now, there are no signs of updates for the Galaxy S21 right now. Once you update your device, you will see an eSIM manager in One UI settings, which will help you to switch between network.
Source: Android Police