In DevOps, it is not always about just piciking the right tool, but understanding what is happening also in terms of the workflow.
Interesting aspects are here delivered value (like saved time) and how the process can be scaled if you get more customers.
Without knowing further details, I would suggest to investigate what your customers do after they have got the release.
Do they use it to install at their workplaces? In this case, customer-friendly mechanism is some sort of autoupdate through update site or providing a link to a CDN, content delivery network service (you just distribute your releases after all as binary content).
Or, are these customers technical users, like system engineers, who have to upload the releases which are actually system components to further FTP interfaces? Here you might want to find out whether it makes sense to investigate seamless integration with their content delivery pipeline.
Or, are these releases executable installers? In this case, you might consider something either like a Bamboo Deploy Plan or integration with customers' configuration as code system (like Chef or Puppet).