Jon Barratt

This appears to restore the previous conditions of output via functions –

add_filter( 'woocommerce_get_availability', 'wc_hide_status_no_manage', 1, 2 );
function wc_hide_status_no_manage( $availability, $_product ) {

    if( $_product->is_in_stock() && get_option( 'woocommerce_manage_stock' ) !== 'yes' ) {
        $availability[ 'availability' ] = '';
    }
    return $availability;
}

I welcome any simpler alternatives ??

Another useful plugin might be WP Clips which also creates a plugin environment for customizations https://wpclips.net

You could always try using a custom Clip for customizing child themes – https://wpclips.net – might be helpful.

I know it’s been a while since you posted, but you could try using a Clip – wpclips.net – I developed the plugin to safely customize plugins and child themes of base/starter frameworks. Really easy to use.