The supported activities are:

edit

Show a connection editor that supports adding, modifying, viewing and deleting connections. It provides similar functionality as nm-connection-editor.

connect

Show a list of available connections, with the option to activate or deactivate them. It provides similar functionality as nm-applet.

hostname

Set the system hostname.

Corresponding to above activities, nmtui also comes with binaries named nmtui-edit, nmtui-connect, and nmtui-hostname to skip the selection of the activities.