Is this lab power supply linear or switch mode type?
Its a linear supply. The manual you linked has as image of the unit displaying a 3303s badge. Looking up the datasheet for that model confirms its linear. As others have mentioned the transformer and series regulator also points to this.

For bonus points, feel the weight of the unit. Typically linear supplies with output current ratings like this have pretty hefty transformers so if your arm aches its most likely linear

Datahseet here: Datasheet