The router does not have an integrated SIM card slot and is primarily designed as a DSL router. It is therefore not possible to insert a SIM card directly into the router.

However, the Speedport Smart 4 can be used in conjunction with a separate 5G receiver to receive Internet via mobile communications (LTE/5G). However, this use requires a DSL connection as the main connection, as the 5G receiver serves as an add-on or backup. This router is not intended for operation with just a SIM card without a DSL connection.