Maybe the Amazon stick has been removed from the trial and no longer works with BBC iplayer in UHD and HLG, that would be very annoying.
I really hope they do transmit the "Seven Worlds, One Planet" in UHD. Sport doesn't really do it for me.
Whilst waiting for the Fire TV Stick 4K Ethernet Adaptor, I've been playing around some more. Setting the Display settings to "Auto" does not work and I've read elsewhere it doesn't. HDR does not kick in and no amount of HDMI input toggling resolves this either. The buffering seems to have been sorted - every time so far that I've tried the Fire TV, it's been immediately after viewing my Roku and, as recommended, have left it plugged in. Yesterday I unplugged the Roku (can't remember why lol) and subsequently enjoyed lovely Wimbledon Centre Court action in UHD HDR. I had set the Display to 2160 60Hhz. PQ was superb as with the Roku and didn't require any HDMI toggling. So maybe, as you cannot "switch off" the Roku that it hogs my broadband's bandwidth for a bit? Strange. But perhaps the removal of the Fire TV from the list of BBC's supported devices could be down to the "Auto" display setting not functioning?
Hopefully I will get the adaptor today.
Never did get the Adaptor but yesterday I'm afraid I watched the magnificent British GP and the awesome Cricket World Cup Final, the latter which will live with me forever! So the marathon Wimbledon Men's Final (which probably would have bored me to death) did not fearure yesterday - Sky ruled for once!
I certainly found the Wimbledon UHD HDR coverage impressive and it showed a long Men's Final in all its glory. Once I did have an issue with buffering but resetting the connection solved it. The only thing is that you cannot pause or rewind and only the HD is available on demand, however maybe that will change in the future.