I just upgraded a WordPress site from 7.4 to 8.0 and in 8.0 got a critical error notice. I enabled debug and debug logging and there was no error display or error logged.
After troubleshooting through the plugins and theme I found an undefined function that was hooked to an action in WooCommerce:
add_action( 'woocommerce_before_add_to_cart_quantity', 'rnr_qty_front_add_cart' );
This action was ignored in php 7.4 but triggered a critical error but with no WordPress debug information in 8.0.
I'm wondering why this is the case?