Personally, I would just put gnolls under the umbrella of "orc-like evil race" and just use the same de-evil steps. Like, take the WoW orcs. They went from evil berzerker types with demon magics to a shamanistic tribal types. Same thing with gnolls.
Do you mean in universe or as how their fiction is written. Because its not the same thing, at all.
Gnolls, under the current iteration of the fiction, are literally just hyenas that became humanoid because of being infused with demonic energies (and quite a lot of demons have humanoid shapes). If it weren't for the demonic energy fueling them, they would just revert back to being hyenas presumably enough.
Within WarCraft, the Orcs were a naturally occurring people, the descendants of the descendants of the descendants of the descendants of giants who had become smaller, yet more intelligent with every spin-off race that occurred from this family line. They were basically smaller, marginally more intelligent Ogres who were in touch with the earth. And bred faster.
Anyway, they found themselves in frequent conflict with the other peoples of their world-- the Ogres, the alien who had appeared from out of nowhere and taken up residence, the bird-people and possibly others I have forgotten... and then they took on the demonic energies that turned them green and gave them quite a bit more bloodlust and savagery than they had before. They remained that way for about a generation before they ultimately got cut off from that source, even killing the original source, and began slowly returning to normal.
But the Orc normal is well... that shamanistic tribal people. Gnolls normal is well... just typical hyena.
Again, if one can say "there is no possible way you can have a good-aligned Rakasha", I just don't really see the issue in acknowledging that because of the way they came about in a single game world that it should be equally impossible for an individual, much less many tribes, of the race to really embrace good.
Then again... given that demonic blood/soul/energy apparently does not remotely hinder Tieflings, I suppose it would be weird for either Gnolls or Rakasha to be entirely without primarily altruistic individuals.
What does it even mean for characters or races to actually be "good" or "evil" when it comes right down to it?
I am not even sure how one even has a society, even a basic tribal one, if literally every single individual within it can mainly or exclusively commit evil acts. I feel like any such society would just utterly collapse. One needs to be at least selfless enough to raise children to adulthood, be loyal enough to one's tribe that they just don't all scatter or end due to massive backstabbing in a short amount of time and not be so primarily interested in inflicting pain and suffering on others that no one wants to live around you or associate with you...
Honestly, I sometimes wonder if D&D just defines "good" and "evil" races simply on whether they happen to be aligned with the protagonist humans or not. Could D&D even do a good or neutral aligned race that are primarily going to be opposed to human interests and generally be at war with humans?
If one is even talking about a "good" Gnoll, are we just saying that the Gnoll would betray all other Gnolls and seek the death of its own people in service to humans and more human-like peoples?