How extensible can I make my installation in terms of sub domains and restricting membership to them?

[tobiaseigen]

If you are self-hosting, you could consider a multisite setup.

Multisite configuration with Docker

While multisite is supported in the Discourse application, this is an advanced sysadmin setup. If you don’t know what you’re doing, do not set up multisite. The Discourse team is unable to provide multisite configuration support. If you wish to host multiple domains on a singled Docker setup, you’ll need a multisite configuration. Here are the basic building blocks for one. Understand hooks Multisite is a fairly advanced topic. Before attempting a multisite build, spend some time…