Now, this is a fairly shit suite of abilities, I'm pretty sure (not sure informed on 5e Balance.
Further, for some fucking reason, 5e completely rewrote gnoll origins to be "Uber-Orcs"(unthinking savages, HARD Chaotic Evil, etc) presumably to make them distinct from other monstrous humanoids, and to contrast them with the lazy depiction given in Pathfinder.
As such, we need subraces, and we need an explanation for how this gnoll is playable as a race.
Clearly, the easiest answer is SPITE.
Gnolls have been Yeenoghu's favored servants for millennia, and the profane rituals that create and continue their 'race' have made him a much desired commodity in Abyssal tactics: an inexhaustible pool of mortal servants, created through the corruption of beasts.
Such power was not to go un-challenged in the Abyss forever. And so, two princes of the Abyss have joined forces, and worked a corruption of their own, based in the very source of the Destroyer's strength: for Yeenoghu may be the Lord of Savagery, but he is not the Prince of Beasts. And while his foul shamans work dark magics, they are nothing compared to the Witch Covens that serve the Dark Prince of the Abyss.
So Graz'zt and Baphomet polluted the great rite of Yeenoghu, seizing some of the new-wrought souls for their own.
But the magics that were used to corrupt his control warped in the arcane fires, In breaking the shackles of control imposed by Yeenoghu, the magic fully freed the new gnolls: while touched by the powers of the Abyss, they did not need to heed it. A Soul-Stolen Gnoll may be of any alignment, though they do tend toward evil and chaos, as few fully escape their dark origins.
Yada yada
subraces
Beast-kin (Baphomet)
+1 Con
Feral Senses: advantage on Perception rolls where smell could be a factor, or whatever.
Witch-Hounds (Graz'zt)
+1 Cha
Proficiency in Deception.
Or something like that.