If you want to stream data inside a HTTP body (of any protocol), then the ReadableStream/WritableStream APIs would be the appropriate APIs (https://developer.mozilla.org/en-US/docs/Web/API/Streams_API) - however at least in the past they have not been fully standardized and implemented by browsers. Not sure what the latest state is.
WebTransport is a bit different - it offers raw QUIC streams that are running concurrently with the requests/streams that carry the HTTP/3 requests on shared underlying HTTP/3 connections and it also offers a datagram API.
WebTransport is a bit different - it offers raw QUIC streams that are running concurrently with the requests/streams that carry the HTTP/3 requests on shared underlying HTTP/3 connections and it also offers a datagram API.