My girlfriend could keep her home phone line enabled while using the eSIM but I couldn’t, even though we have the same model of phone! Turns out her home line uses a physical sim, but mine is set up using an eSIM and the iPhone 12 can only have 1 eSIM enabled at a time. You can do 1 physical + 1 eSIM, but not 2 esims.
I couldn’t get texts or calls from home without noodling with my phone settings each time. And FaceTime kept enrolling and unenrolling my number.