I have a cloud run services using an Assigned by Cloud Run URL.
I tried to setup an SSL certificate with Assigned by Cloud Run URL, to integrate with LB, but the cert status is FAILED_NOT_VISIBLE after provision
You can not set up an SSL certificate with a URL assigned by Cloud Run to integrate with a load balancer. But here is a workaround to integrate a load balancer that utilizes a serverless NEG backend to route requests to your Cloud Run service.
To generate an SSL certificate resource, you can choose between a Google-managed or a self-managed certificate. If you opt for a Google-managed certificate, you must have a domain, and its A record needs to point to the IP address of your load balancer. To set this up, create an A record for each domain through your domain registration service, ensuring that all A records direct traffic to the same load balancer IP address.