Disables Gutenberg for the Widget Area in WordPress

disable-guteberg-widgets.php

// Disables the block editor from managing widgets in the Gutenberg plugin.
add_filter( 'gutenberg_use_widgets_block_editor', '__return_false', 100 );

// Disables the block editor from managing widgets.
add_filter( 'use_widgets_block_editor', '__return_false' );

if ( ! function_exists( 'themename_activate_classic_widgets' ) ) :
function themename_activate_classic_widgets() {
    remove_theme_support( 'widgets-block-editor' );
}
endif;
add_action( 'after_setup_theme', 'themename_activate_classic_widgets' );