Alternatively we can add support to allow $wgOATH2FARequiredGroupRemovalPages to be null and reword message if it is null. (for 3rd party wiki we should not assume such a page exists, so null should be the default.)

		"OATH2FARequiredGroupRemovalPages": {
			"value": [],
			"description": "An array of page names, where user can ask to have themselves removed from groups that require 2FA (keyed by the group name). The pages will be linked in the notice about 2FA being required for user. If there's no entry for the relevant group, key '*' will be used."
		},

If they remove 2FA, they lose access to the wiki...

It would be possible for someone to remove 2FA for them, and then re-set them up with initial codes to keep ongoing access... And then they would need to setup proper 2FA again.

Would it make sense to have a page for that?

Does it make more sense to just have some permanent banner on Special:AccountSecurity (and/or something on Special:Preferences, because if they have to reauth with 2FA, they might not be able to) that 2FA is required on this wiki...

That they can request $someone (ala the removal page) to remove it for them, and/or if they need to remove a 2FA device, and only have one, they need to set up a new one first, to be able to remove the one they want to remove...

I believe the 2FA enforcement work prevents a user from self-removing required 2FA.

For me, makes sense to have a separate notice that 2FA is required on that wiki (that replaces the current "some of your groups require you to have 2FA"), for two main reasons:

• The current notice is meant to tell the user "You can still remove 2FA on this wiki, but you'll have to resign from some of the groups" (after which your account will still be usable etc. etc.). This is not the case for the wiki-wide enforcement. There, it's like "You cannot remove the last 2FA method."
• If the wiki requires 2FA from all users, IMO it might be confusing to see the "user" in the list of one's 2FA-required groups on S:AccountSecurity (especially if it's next to other groups that are removable), as technically one can't be removed from that group. Reducing the size of the message to cover just the case about the wiki-wide enforcement seems like it's good UX.

Given that (unlike with groups, which there are many and managed on a lot of different pages), I think any help page links (if needed) in such message can be embedded directly into the message and overriden through the normal on-wiki page in MediaWiki namespace.