Do EVs with a DC motor require an inverter and/or/nor a converter between the battery?
In a DC motor, the frequency of the (also required) AC current is created mechanically, by the turning of the rotor and the work of the commutator.

The most energy-preserving way to control the torque of a DC motor, and thus, the speed of the drive, is to adjust the voltage. Today this is done by using a buck converter.

You may want to look up pre-1960ies electrical locomotives for information about how it was done before power electronics.