https://www.kustomer.com/

It’s a service they’re subscribed to running as a subdomain on the providers domain.

It’s just not built for that. It’s heavily focused on being a client. It has some passable server functionality, but they don’t really make design decisions based on that use case.

Server OS is more designed for that purpose, and most people pass on that because it just costs so much more, and their are free or very low cost alternatives.