This has probably been answered somewhere else before so I apologize in advance. Does Unity’s integrated multiplayer solution allow you to host a local game on WebGL? I can see that there is an option to use web sockets for the NetworkManager, however, it only mentions connecting to another server, not hosting one yourself.
No, that is not possible. WebGL runs in a security sandbox. Your browser doesn’t allow webcontent to open a listening socket. Since a WebGL game is usually hosted on a server you would need to host a server there where the players can connect to. You also can create a standalone build which acts as server.