A live sports score page pushes score updates to thousands of viewers. Viewers never send data back over the channel. Which transport fits best?

Server-Sent Events (SSE) fit best. The traffic goes one way, from server to client. SSE gives exactly that over plain HTTP, with reconnection built in. "WebSockets" is the tempting wrong answer. They would work, but they add two-way machinery and reconnection logic that this page does not need.