I too am having issues launching Greedfall on Xbox One X. I do believe I figured out the problem, however.
I tried what some have suggested. Going to the Xbox One X settings menu, selecting Display and Sound, then selecting Video Output, then selecting Video Modes and finally unchecking the Allow 4K toggle.
After following these exact steps, Greedfall launched fine for me. Afterwards, I changed the settings on my Xbox One X to allow 4K content again. As soon as I did this, I attempted to re-launch Greedfall and it crashed my Xbox One X.
Whatever this issue is, it is directly tied to the setting allowing 4K content on the Xbox One X. If the setting is toggled on to allow 4K content, Greedfall will not launch on Xbox One X.
Please look at this and fix this, Spiders! PLEASE! I want to play Greedfall SO BAD and it pains me to have to constantly be adjusting my console settings just so Greedfall will launch.