Sure, but those will usually be pieces of an app on the same host, not whole apps. Like for an inventory management app, you might have the auth server and its database on one host, the CRUD app and its database on another, and the report server, its database, and a replica of the CRUD db on another. And I use the term “host” broadly enough to include VMs on the same physical hardware. And these hosts will have restricted communication between each other.

At least, that’s how I’ve seen it done.

Self-hosters will generally run multiple full apps on one host. It’s a different setup.