Gornog, the Red Reaper can target non creature permanents.

[Tharkon]

When attacking with [Gornog, the Red Reaper] or another warrior while it is on the field I can select any permanent controlled by defending player, not just a creature.

Choosing a non-creature permanent appears not to do anything but might do something if that permanent would become a creature later in the turn. Either way, it should not be a valid target.

[JayDi85]

[[Gornog, the Red Reaper]]

[github-actions[bot]]

Gornog, the Red Reaper - (Gatherer) (Scryfall) (EDHREC)

{2}{R} Legendary Creature — Minotaur Warrior 2/3 Haste Cowards can't block Warriors. Whenever one or more Warriors you control attack a player, target creature that player controls becomes a Coward. Attacking Warriors you control get +X/+0, where X is the number of Cowards your opponents control.