In v4-only world some of these cellular devices already implement NAT
and DHCP server to share to LAN the single IPv4 address they got from
the network via point-to-point link. In v6 they should implement ND
proxies and DHCPv6 PD (to avoid need to do IPv6 NAT). For providing IPv4
connectivity for legacy devices in LAN when having only IPv6-native
access network, these devices shall implement some of those
IPv4-over-IPv6 technologies and then NAT the IPv4 address obtained e.g.
with DSMIPv6, MNAT-PT etc. for the devices in LAN and RFC1918 space.