Solution for Widgets Not Working After Upgrading to WordPress 5.8

After the WordPress 5.8 update, the default Widgets in the Admin Dashboard now use the Gutenberg editor for management. Some older themes may have compatibility issues, causing the page to not open or display a white screen when setting up Widgets. To solve this problem, we can switch the Widgets back to classic mode. WordPress has specifically released the Classic Widgets plugin for this purpose; you just need to install and activate it.Plugin DownloadIf you don't want to use a plugin, you can also directly copy the code below and add it to the theme's functions file.

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

Description

Classic Widgets is an official plugin maintained by the WordPress team to restore the previous („classic”) WordPress widgets settings screen. It will be supported and maintained at least until 2022. After activation, this plugin restores the previous widgets settings screen and disables the block editor for managing widgets. There is no other configuration; enable or disable the classic widgets settings screen by enabling or disabling this plugin. Related articles:

• How to Disable the New WordPress Gutenberg Editor