Is it possible to link more than 1 SSL certificate to an Elastic Beanstalk ALB?
I understand that one can create a bundle domain certificate in Certificate Manager, but I would ultimately want to give my clients the ability to add their own domain pointers pointing to the EB environment.
Yes, you can do this. Probably not from EB console, but you can deploy multiple SSL certs on ALB as explained in:
You would have to go to EC2 console -> Load balancers, and work with the ALB there. Obviously you could do the same things using AWS CLI or SDK if you want to automate things.