As someone who uses a custom domain for Proton Mail, I would like an option to setup a custom domain (or subdomain) for Proton Drive.

Ideally a custom domain would be usable for both logged in Drive users and share links, but at a minimum there should be a way to select custom domains when creating share links.

For example, if I am using a "username@domain.example" email address in Proton Mail, I should be able to generate share links that start with: https://drive.domain.example/urls/[...] instead of: https://drive.protonmail.com/urls/[...]

I know SSL may make this feature more difficult or costly to implement securely, so it could either be a premium feature (with an added recurring cost) or require that the account holder upload a valid SSL certificate for the domain.