Mostly... SPOILERS - The Vision has been re-built, but lacks the emotional attachment to his memories / relationship with the Scarlet Witch. (Something similar happened in the comics awhile ago.) - "Our" Loki (the one from the MCU) still died in Avengers: Infinity War. A variant of that same character escaped with the Tesseract / Cosmic Cube during Endgame, and is the Loki that is still running around in the MCU....which is now seemingly under the control of a different Kang variant, causing a whole lot of multi-verse issues for the next batch of films. - The comics version of the Black Knight (Kit Harrington's character in Eternals) doesn't have powers directly, but his sword allows him to be resurrected if he dies while holding it. No telling if any part of that makes it into the film. He's not actually one of the Eternals, though. So far as I can tell, he shows up because he and one of the Eternals (Sersi) had a thing in the 90's Avengers book....which I hope gets adapted differently than it was back then. - The What If series is showing us different variations allowable by the multiverse (like Into the Spider-Verse did for Spider-Man, but with much more limited licensing rights). After Loki, it's hard to say whether any of it is particularly important, or just Easter eggs all the way down. Still fun, though. - Falcon is Captain America now. - A potentially more fun version of Hawkeye is coming to Disney+ in November. - Though Marvel hasn't said so explicitly, they seem to be laying all the groundwork for a "Young Avengers" spin-off. Disney+ will give you access to everything (which is great for the nerds like me who grew up with the Marvel characters back when only DC Comics characters got movies). The films should bring you up to speed on as much or as little as you need to know.