I ran some tests and it looks like the game recognizes Gnawing Hunger as a void weapon, but the Seasonal Artifact somehow does NOT as the mods show "This perk will be enabled when you equip a void weapon" when Gnawing Hunger is the only void weapon you have equipped. I tested on Neomuna Terminal Overload and confirmed Gnawing Hunger isn't proc'ing ANY of the Seasonal mods that are activated when you equip a void weapon (Void Weapon Channeling, Bricks from Beyond, Volatile Flow), unless you have another void weapon equipped as well. With any of my void weapons in the Heavy slot then all the void-specific Seasonal mods start working for both void weapons. I also ran the same tests with Age-Old Bond (also a void auto-rifle), but that weapon worked just fine. With Age-Old Bond as the only void weapon equipped all the mods proc'd when expected and the void-specific mods didn't have that "This perk will be enabled when you equip a void weapon" message appear in the Seasonal Artifact screen.

Are people also running the anti overload champs mod as well? Havent bothered to check yet but I feel like that might counter the other mod

Hasn't worked for me either.

Huh, I did wonder as ive had Gnawing Hunger running and rarely noticed volatile activating.

after they said they where buffing auto's i pulled this out to be disappointed that it wasnt working with the artfact mod for picking up orb of power.