app/Logging/JsonFormatter.php

<?php

namespace App\Logging;

use Monolog\Formatter\LineFormatter;

class JsonFormatter extends LineFormatter
{
    public function format($record)
    {
        return json_encode($record);
    }
}

app/Logging/JsonFormatterApply.php

<?php

namespace App\Logging;

use App\Logging\LineExFormatter;

class JsonFormatterApply
{
    public function __invoke($logging)
    {
        $exFormatter = new JsonFormatter();

        foreach ($logging->getHandlers() as $handler) {
            $handler->setFormatter($exFormatter);
        }
    }
}

config/logging.php

    'channels' => [
        'stack' => [
            'driver' => 'stack',
            'channels' => ['bugsnag', 'daily'],
            'tap' => [
                App\Logging\JsonFormatterApply::class,
            ],
        ],