I have a plasma TV and in its menu black levels can be adjusted. Adjusted to its highest level it compensates the dark screen problem. Hopefully a future update will negate having to adjust TV settings. Nevertheless I'm happy with box but hope for a firmware solution in the future.
I have both a Samsung and an LG 4k tv [55KU6092 and 55UH605v]
the dark screen is present only on the samsung. it can be fixed by playing a 4k or by enabling the Hdr+ option on the TV.
However other issues are also present when playing on the samsung [playback stutters on movement on all the players, worse juddering]. If I play the videos directly from the TVs via Plex these issues are not present and videos play similary on both tvs.
all in all playback it's much worse when connected to the samsung even tough the samsung it's slightly better when connected to any other source but the GT1.
in my previous post when I said it is present on the samsung but not on LG it was because I only had HDMI CEC enabled on the samsung. as soon as I enabled it on my LG dark screen problem appeared.
@steelgtr. Switch off acceleration for amlogic and surface in video settings. This allows you to set contrast and brightness on video playback. This is done when playing video, pull up the playback bar. Go to picture feel icon and you will see adjustment options.