I had to uninstall KB5006670 - on WinVer 20H2 - 10.0.19042 N/A Build 19042
MSFS would get to the main menu, but when i created a quick flight on the world map, it would start loading and then freeze…
start > Settings > Update & Settings > View Update History > Uninstall Updates (at the top of screen)
Thank you for sharing this finding. I had the same issue with KB5006670 and 21H1. The sim freezed during loading a flight. It worked again after removing this update. Btw, I used the FBW A32NX experimental.
Update: I reinstalled KB5006670 and can still start flights without issues. Maybe something went wrong with the first install of the update or just the reboot helped