Do I need a hub to use a smart plug?

For almost all of the picks here, no. Wi-Fi smart plugs from TP-Link (Kasa and Tapo), Govee, and Amazon connect directly to a 2.4 GHz home network and pair with Alexa or Google Home through their respective apps. Matter-over-Wi-Fi plugs like the Tapo P125M technically benefit from a Matter controller (a HomePod, Echo, or Google Nest hub you likely already own), but they don't require a dedicated smart-home hub like Zigbee or Z-Wave plugs do.