I don’t think RTSP is supported. I didn’t try it but our Livestream feature is based on RTMP, also as you mention streaming in 4K is not currently available.
You are right, sorry for misunderstanding. We do support 4k 60fps in H264 but not H265 because as you mention RTMP I think doesn’t support it.
After consulting with the team, what is mentioned in this article is more about VOD and not LiveStream.
Although I did a LiveStream using OBS with the following resolution 3840x2160 (it works), we can’t confirm that the QoE will be the best in delivery, it depends on many things.
I definitely recommend you to try it for yourself using sandbox and see if it fits your needs.