windows.security.authentication.onlineid: Implement IOnlineIdSystemAuthenticatorStatics::get_Default().
I originally added this for Minecraft Education Edition to see if it would help with a sign-in issue, but it didn't seem to so I didn't create an MR for it. But this library is also used by Office and other apps. For Office, there are 2 reports[1][2] that say this is the cause of an installation crash. I can't confirm it as I don't have an Office subscription.
I have some more patches for this that Minecraft Education Edition calls but I don't know if they're helpful for Office.