Hi Andrew. Note that the (supported) containeir image itself is based on Centos7, but you may use a different one, there's some info about it on the manual: https://help.tableau.com/current/server-linux/en-us/server-in-container_setup-tool.htm#customizing-the-image (scroll to “Defining a Custom Base Image”).
If you do choose a different base image (e.g. due to a security mandate), then you need to ensure Tableau Server runs well on it .
Note that running a container is possible on any enterprise linux, including Ubuntu.
In reality, most companies will not be using Docker itself for production use, they will be using Kubernetes, and often be using a managed K8s solution like AWS EKS or Azure AKS, where the host operating system is determined by the cloud provider and not really relevant, the container just works.
Hope this helps?