A computer with a modern operating system and networking software can host the wiki server. This combination of resources can be found in many places.
See also Federating Foreign Servers
Laptops you already own.
Servers designed for many services.
Virtual Machines configured for one thing.
PaaS cloud services.
Docker containerized packages.
A host can run many servers and a server can serve one or many sites.
Development with multiple servers.
Farms with many sites served by one server.
Security for authenticating site owners.
Update with improvements from open source.