How to manage pointing custom domains for whitelabelled SAAS application to the same ec2 instance?

Question

We are running a SAAS application that provides support for custom domains. We had been managing this by adding HTTPS listener for each domain at AWS Application Load Balancer and adding a corresponding certificate for the said domain.

We are facing issues with this -

1. Everytime a new customer is added, we have to do this manually.
2. The AWS quotas are limiting our abillity to onboard new clients as we look to scale.

Can someone suggest a better approach to handle this? Can we use Route 53 to add all the custom domains and map it once to the Elastic Load Balancer? And how to do this dynamically?

We are exploring adding multiple Load Balancers when quota limits exhausts but are unsure about this aaproach.