Configure MultilingualPress to only redirect users on the front page

mlp-redirect-on-front-page-only.php

<?php # -*- coding: utf-8 -*-

add_action( 'inpsyde_mlp_init', function () {

	remove_action( 'inpsyde_mlp_loaded', 'mlp_feature_redirect' );
} );

add_action( 'mlp_and_wp_loaded', function ( Inpsyde_Property_List_Interface $plugin_data ) {

	if (
		is_admin()
		|| parse_url( trailingslashit( home_url() ), PHP_URL_PATH ) !== trailingslashit( $_SERVER['REQUEST_URI'] )
		|| ( defined( 'DOING_AJAX' ) && DOING_AJAX )
	) {
		return;
	}

	$response = new Mlp_Redirect_Response(
		new Mlp_Language_Negotiation(
			$plugin_data->get( 'language_api' ),
			new Mlp_Accept_Header_Parser(
				new Mlp_Language_Header_Validator()
			)
		)
	);
	add_action( 'template_redirect', [ $response, 'redirect' ], 1 );
} );

This should work too.

add_filter ( 'mlp_redirect_url', function( $redirect ) {

    return parse_url( home_url(), PHP_URL_PATH ) === $_SERVER['REQUEST_URI'] 
        ? $redirect : false;
});

This gist is intended to be used when you want to completely deactivate the Redirect feature altogether, and only want to redirect your users from your sites's individual front page.

Using parse_url( home_url(), PHP_URL_PATH ) === $_SERVER['REQUEST_URI'] instead of just '/' is a very good idea, though. I just made this gist for a customer, assuming a standard subdomain install, not in a subdirectory.

I'll adapt this.