Business networks typically had manually provisioned subnetwork prefixes.
Once assigned, the ISP routes this network to the customer's home router and the home router starts advertising the new address space to hosts on the network, either via SLAAC or using DHCPv6.
DHCPv6 Prefix Delegation is supported by most ISPs who provide native IPv6 for consumers on fixed networks.
Prefix delegation is generally not supported on cellular networks, for example LTE or 5G.
Most cellular networks route a fixed /64 prefix to the subscriber.