Use the model diagram and confirm the collection arrangement before removing anything. A visible cap elsewhere on the cabinet may serve a different purpose.
What the observation tells you
Some freezers have an owner-operated drain; others require water to be collected another way. Removing an unfamiliar plug can cause uncontrolled leakage or disturb a component. An illustration for a different chest freezer is not enough to identify yours.
A useful next step
Prepare suitable water collection and follow the exact instructions. Keep electrical connections protected and refit the intended drain components afterwards. If a plug is missing or damaged, obtain the correct replacement rather than improvising a seal.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.