Summary
The nextStar Trekseries,Star Trek: Starfleet Academy,can finally explain the variant Klingons inStar Trek: Discovery. There have beenmultiple versions of KlingonsoverStar Trek’s nearly 60-year run because of advances in special effects makeup technology since the 1960s. AfterStar Trek: The Original Series' smooth-headed Klingons, characteristic forehead ridges appeared on Klingons inStar Trek: The Motion Picture,and even then, the most popular modern Klingon look wasn’t finalized untilStar Trek: The Next Generation. AfterStar Trek Into Darknessevolved Klingon makeup beyond theTNGlook,Star Trek: Discoverypushed Klingons even further, making Klingons even more distinctively alien.
According toStar Trekcreator Gene Roddenberry, theKlingons were always supposed to have a more alien appearance than what was seen inStar Trek: The Original Series,and the higher budget ofStar Trek: The Motion Pictureis what allowed that intended vision to finally be realized. Still,Star Trekwanted to explain the changes to the Klingons' appearance with an in-universe reason, which was finally provided inStar Trek: Enterpriseseason 4, episode 15, “Affliction”, when theNX-01 Enterprise crewdiscovered that Klingons' attempts to create their own Augments resulted in a deadly virus, and the cure left affected Klingons with a markedly human appearance.

Star Trek’s 10 Greatest Klingons
Star Trek has many great Klingon characters from Kor to Worf and Kruge to Torres. But who are the best Klingon warriors that Qo’noS has to offer?
Starfleet Academy Can Finally Explain Star Trek: Discovery’s Klingons
Starfleet Academy’s Educational Setting Can Canonize One Of Many Klingon Theories
Star Trek: Starfleet Academycan do forStar Trek: Discovery’s Klingons whatStar Trek: Enterprisedid for the Klingons of theTNGera, and offer an in-universe explanation for the changes to Klingons.Star Trek: Discoverywas never concerned with explaining the changes to Klingons, since its focus was on moving plot and character forward instead of stopping for lessons in history or xenobiology.Star Trek: Starfleet Academytakes place at a school, so there will be natural opportunities for lessonsthat can educate viewers and Academy cadets at the same time, just like Doctor Erin’s (Dr. Erin Macdonald)Star Trek: Prodigytemporal mechanics explanation.
There are several theories that can explain the differences inStar Trek: Discovery’s Klingons. An attempt to reverse the effects of the augment virus fromStar Trek: Enterprisecould have overcorrected the Klingon features, resulting in the more pronounced alien visages seen inStar Trek: Discovery.Mary Chieffo’sDiscoveryKlingon theorysuggests L’Rell leads"an ancient sect of outcasts"far removed from the Klingons of Q’onoS, which also explains the differences in culture.A theory dating all the way toStar Trek: The Motion Picturesuggests multiple variations of Klingons all co-exist in the timeline, but hail from different regions or colonies in the Klingon Empire.

Star Trek: Strange New Worldstakes place in the mid-23rd century, likeStar Trek: DiscoveryandStar Trek: The Original Series, and depictsTNG-era Klingons, suggesting that all 3 variations of Klingons exist at the same time.
Why Star Trek: Discovery Avoided Klingons After Season 3
Can Starfleet Academy Also Explain What Happened To Klingons In The 32nd Century?
With a jump into the 32nd century,Star Trek: Discoveryseason 3 was a soft reboot that attempted to avoid the pitfalls ofDiscovery’s first 2 seasons, and that included not even touching the controversial Klingon redesign. Rather than attempt to explain whyStar Trek: Discovery’s Klingons were different, or show how the Klingons might have evolved in the 900 years since the USS Discovery’s point of origin,Star Trek: Discoveryavoided showing any Klingons at all in the 32nd century.This allowedStar Trek: Discoveryto focus on telling new stories in a new era, but also raised questions about what might have happened to the Klingons in the intervening centuries.
The lack ofKlingons in the 32nd centurymakes sense from a production standpoint, butStar Trekmight also be able to explain why there aren’t any Klingons inStar Trek: Discoveryfrom season 3 onward.It might not be as simple asStar Trek: Discovery’s Klingons being just offscreen. Klingons might have become extinct thanks to centuries of prioritizing war. The Burn may have made Klingons isolationist and xenophobic. A completely new catastrophe may have befallen the Klingon Empire before the 32nd century. A crash course on Klingons inStar Trek: Starfleet Academycould reveal the Klingons' fate, and also explain whyStar Trek: Discovery’s Klingons were so different.

