This idea is strengthened by the fact that Discovery and Strange New Worlds are clearly shown to take place in the same universe, with Discovery introducing the characters and ship that appear in Strange New Worlds, and Spock from Strange New Worlds reflecting on the events of Discovery. And SNW later shows TNG style Klingons, establishing that both styles (as well as presumably TOS style Klingons) coexist in the same universe. So I don't think the Lower Decks episode resolves anything about the Klingon-look at all, it was just a fun reference/gag.
It could be that the shows exist in different timelines, but it could also be that any of the shows exist in different timelines that are just similar enough to make the references make sense. For instance, Lower Decks establishes that a Picard exists in it's universe, but also exists in many other universes (see the purple enterprise), so it doesn't necessarily take place in the same universe as TNG.
Genuinely this is really good headcanon though -- a great illustration of why canon matters as an imagination tool.
Correct, but how that proves that Discovery in the main universe does not exist? We seen a Garak for an other universe and that does prove that you can have same people , same ships, same uniforms in different universes, this was shown durin TNG.
So the only thing proven is that Discovery exists in a different universe, it is not proven that it does not exist in the main universe.
Let me know if my logic is wrong, we can try and formalize it better using any, exists, implies etc .
Given that Lowerdecks is an extremely canon-oriented fan-service love letter to earlier shows that are known to be canon (ie, that it demonstrates consistency with obvious canon like TOS and TNG) the hypothesis that it's NOT in the main universe seems to be the one that requires a proliferation of assumptions and therefore more argumentation and data to support.
I think it would make sense Disco is different universe , would make the fans happey too , but this episode brings no proof for it , though in a trek form or reddit I would let the fans to enoy this "fake news" , here or in Daystrom subreedit I am though expectic more logic.