See screenshot. By default, none of them were selected. Selecting any of them doesn't make any change. This stands to reason as Verizon is not my actual carrier.
I think this is as close to an explanation as I've heard so far. So then is this something missing from the upstream LineageOS? Is there anything I can do about this? Some searching says that one can add/edit APNs from within the interface, but is there any way to tell what I should use?