The require_once in `admin/tool/mfa/factor/email/email.php` is invalid. In some edge-cases, it can cause PHP to require the config.php file twice, since as written, it's including:

Two issues - it has one set of dots too many for the depth.

And {}DIR _does not end in a slash, so if }}{{DIR_ was /app then it results in requires that look like:
/app../../../config.php - which is obviously wrong.{{}}

Steps to reproduce:

For a test system under /var/www/moodle, rename the config.php file, then symlink to it, something like:

Restart php-fpm, or apache, to ensure the realpath cache is cleared.

Browse to: admin/tool/mfa/factor/email/email.php?instance=1

You should see an "unauthorised email" message. Without the fix, you may instead see a bunch of errors that indicate config isn't loaded properly.