Steps to reproduce the issue

Install Joomla 4.2.0 on a server without GMP and bcmath PHP Extensions
Login to Joomla Admin and Enable Multi Auth using an Web Authentication (Touch ID on Mac)
Joomla allows this, and secures your account.

Logout

Attempt to login again

Expected result

Expect to be prevented from locking myself and users, out of their accounts

Expect not to be able to SET UP and LOCK an account if the server then cannot authenticate that multi-auth authenticator due to server requirements not being met.

Actual result

Im now forever locked out of my account because I was allowed to enable multi-auth but my server doesn't have GMP or bcmath extensions and so I cannot login on the captive login page