Hey everyone! In July 2021, WordPress 5.8 was released, and with it came a few bug fixes and changes in process.
One of the major issue is in the widget section (appearance-> widgets). You may already experienced that your widgets are not loading in the backend widgets area or error appearing (not working) . This is an issue because the new WordPress 5.8 widgets are now uses and managed from the block editor.
To over come this issue you need to upgrade your theme by including the block editor support for widgets. There was a lot of feedback given in the support forums, and the WordPress team has given 2 best solutions for this until you solve the theme support for this new update.
WordPress 5.8 widgets issue : Solution 01
WordPress 5.8 widgets compatibility issue : Solution 02
As of WP 5.8, block editor is enabled by default in widgets, you can disable this by using the filter below from the wp-config.php file.
add_filter( 'use_widgets_block_editor', '__return_false' );
You may see some forums suggesting solutions like to disable themes or downgrading WordPress version etc. with above solutions you don’t need to bother with that kind of tweaks and it could ended up with some more unexpected errors with other functionalities.