Yes, this will work while traveling. I did the same thing while traveling in Europe this year but used the eSIM with KnowRoaming for my Data and my primary SIM card was still used for my phone calls and texts. Everything worked fine.Another thought given this is an old thread - I wonder if switching to use an eSIM for my primary line, that when I travel I can use a local sim for data / calling and my primary number will still be registered with iMessage via the eSIM?