Okay, so I found a plugin called Force Email Login, though it hasn’t been updated since WP 4.7 (3 years ago I believe, if my Spanish is still working)… .

It seems to work with no issues, works quite nice, but the only code the plugin has is this:

<?php
/*
Plugin Name: Force Email Login
Author: Takayuki Miyauchi
Plugin URI: https://github.com/miya0001/force-email-login
Description: Use email address for login to your WordPress.
Version: 0.6.0
Author URI: https://miya.io/
*/

$force_email_auth = new Force_Email_Auth();
$force_email_auth->register();

class Force_Email_Auth {

	function register()
	{
		add_action( 'plugins_loaded', array( $this, 'plugins_loaded' ) );
	}

	public function plugins_loaded()
	{
		remove_filter( 'authenticate', 'wp_authenticate_username_password', 20, 3 );
		add_filter( 'authenticate', array( $this, 'authenticate'), 20, 3 );
	}

	public function authenticate( $user, $username, $password )
	{
		if ( is_a( $user, 'WP_User' ) ) {
			return $user;
		}

		if ( ! empty( $username ) && is_email( $username ) ) {
			$user = get_user_by( 'email', $username );
			if ( isset( $user, $user->user_login, $user->user_status ) ) {
				if ( 0 === intval( $user->user_status ) ) {
					$username = $user->user_login;
					return wp_authenticate_username_password( null, $username, $password );
				}
			}
		}

		if ( ! empty( $username ) || ! empty( $password ) ) {
			return false;
		} else {
			return wp_authenticate_username_password( null, "", "" );
		}
	}
}

Yet, far as I can tell it should work with WP 5.2.4 (I don’t want to upgrade to WP 5.3, just not feeling it LOL).

It seems to work well with all of your BuddDev plugins… .

Thank you.