Reading through the docs and some past help questions left me a bit confused.
Docs indicate that streaming requests are supported for opus and that encoding can be set to opus
But docs (and another support reply that I've seen here) indicates that opus should not have encoding or sampleRate set as parameters because that's only for raw audio.
The distinction is important though: opus is neither raw audio nor a containerised format. .opus files are normally ogg-containerised, while the raw opus streaming format needs to be separated by frame because it is encoded and otherwise has no boundary segmentation
So what's reasonably clear to me is that raw audio is supported in streaming, and opus-encoded ogg files are also supported in a streaming format -- but what about streaming of raw opus frames?
Testing with the streaming websocket (using both ?encoding=opus&sampleRate=24000&channels=1 and without specifying any params) yields no transcription replies at all, so I think the answer is no.