As per official wording yes it's canon to MCU
“Moon Knight is very much in the MCU,” executive producer Grant Curtis
tells Inverse. “The observant viewer is going to hear and see those
Easter eggs we drop that do explain that and confirm that.”
According to Curtis, the lack of overt connective tissue between the
series and other MCU projects simply follows what the source material
inspires. More often than not, the source kept Moon Knight away from
the superheroic heart of the Marvel comic book universe.
“We looked at the very first comics he appeared in, in 1975, and we
looked over the years of storytelling, over the decades of Moon Knight
stories, [and asked] what are the themes and tones that we’re
gravitating towards as storytellers?” Curtis says. “We never
intentionally tried to make this standalone.” - Inverse
And the afterlife existed already in MCU and was mentioned in Black Panther, which is indirectly connected to Moon Knight:
The name-drop occurred when Steven and Marc boarded Taweret's boat
after being shot by Arthur Harrow, going across the sands of the Duat
to see if they could gain passage into the celestial Field of Reeds.
As they spoke about being dead with the hippo-goddess, Taweret, she
confirmed this was no illusion -- these realms exist for folks who die, but they're seen in different ways in various cultures.
She then spoke of the gateway from Black Panther, name-dropping the
Ancestral Plane. Taweret was clearly in awe of it, calling it
"gorgeous," which fans did witness in the first film. There, King
T'Challa took the Heart-Shaped Herb, allowing him to transcend to the
ethereal field where he spoke to his dead father, T'Chaka. - CBR
So the afterlife exists in marvel and it will be visualized based on that person's culture.