The error appears indeed if you don't have an amqp connection configured to point to rabbit message broker. And will appear indefinitely (if you don't set up the connection) as this is triggered by a Magento cron which processes the bulk update operations (please refer to https://devdocs.magento.com/guides/v2.4/extension-dev-guide/message-queues/bulk-operations.html for further details).
If you don't use bulk operations at all, you can omit installing rabbitmq, but you will see that error log message forever. But if instead you are using bulk operations in your project, then you MUST install rabbitmq, otherwise, these operations won't be processed at all.
LE:
The official documentation says you have to add the queue section in the app/etc/env.php file, but if it exists, you just have to add under it the amqp key and configure it. It will look something like this:
[
(...)
'queue' => [
(...)
'amqp' => [
'host' => '<rabbitmq_host>',
'port' => '<rabbitmq_port>',
'user' => '<rabbitmq_user>',
'password' => '<rabbitmq_pass>',
'virtualhost' => '/',
'ssl' => true
],
]
]
Now, if you check the registered consumers from a vanilla Magento installation, you will see that only the async.operations.all one is set to have an AMQP connection:
<consumer name="async.operations.all" queue="async.operations.all" connection="amqp"
consumerInstance="Magento\AsynchronousOperations\Model\MassConsumer"/>
all other default consumers will be processed by from the db registered queues and will have no interference whatsoever with rabbitmq. they will continue to work as they did before you configured your amqp connection - only the bulk operations will be processed via the queue registered in rabbitmq.