I've been asking the question in the Radxa telegram group and forum. They have now updated the downloads page to say that LibreElec is coming soon:
There is no known contact between people in our team and Radxa. So I guess they will hack something up based on the current early alpha images and then we will have to disown it because we'll have no knowledge of what got added. NB: We're still in the middle of rewriting the V4L2 driver and associated stateless interface code in ffmpeg so there will be no beta or full release LE 9.0 images for RK3399 - it will remain in Alpha.