Since VoLTE became a thing, OEMs have had to go through specific testing and apparently expensive certification with each network (in every region where they want to market the device) in order to implement the network’s VoLTE spec.
Until 3G started shutting down everywhere, some OEMs likely didn’t bother implementing VoLTE on every device, for every network, in every region, probably reasoning that their phones could still get by (more cheaply) with 3G or 2G calling. That’s not possible in the U.S. anymore, and in some other regions as well.
The interesting thing about the L5’s BM818-A1 modem is that it was designed for automotive uses, which is probably why T-mobile recognizes it and authorizes it; it must have already been certified for that network, and apparently not for Verizon or AT&T. (But then T-mobile has always been more BYOP-friendly than the other U.S. networks.)
However, in our Cellular Providers wiki, I see that one person failed to get data working on PagePlus (Verizon’s network). I don’t know what the issue was…maybe Verizon just didn’t authorize it to connect…?
I burned a tmobile sim card months ago, I didn’t follow the directions on when to install in the sim card, so it basically broke my sim card. GOt a new tmobile sim and it worked along with web browsing, albeit slow. Mint mobile I am currently using with a prepaid sim card as like a second line to tinker and play with as I am not yet satisfied L5 is daily driver read and it works fine.