Backend to client communication

I’m writing an app (poker game) that would benefit from notifications from the backend. Basically, when a player finishes his turn the system should tell the other players that the state has changed and they should update.

However, AFAICT, this is not possible and clients have to poll instead.

So, is it still the case today?

I think what these discussions are about is slightly different.
In my case, I would be fine with a void => void function which should not break the determinism requirement.