Have a look under POST Behaviour.

Do they mandate the use of MS Authenticator specifically, though?

The option to add that restriction is definitely there, but it’s worth checking your account settings to see if it’ll let you use a different MFA option.

From what itch.io have posted, I don’t think they’ve been removed as such - they just don’t appear if you browse or search for them.

Direct links should currently still work if people have them.