The ONN model I own (manufactured by Hisense AFAIK) doesn't have all those features, despite having Roku built in..Here's one blurb from a 65" Hisense ROKU...weird I just saw it...
The connector labeled HDMI (ARC) or HDMI IN (ARC) has the additional ability to use
the audio return channel to send digital audio to a receiver or sound bar, as explained
in Connecting an AV receiver or digital sound bar
https://assets.hisense-usa.com/assets/ProductDownloads/202/c8c9a74079/Roku-User-Manual.pdf
I even confirmed that the onboard Roku software has a current up to date software download. The limitations I am experiencing may be related to firmware.
My frustration is from the fact that using the SPDIF toslink digital audio feed from my direct TV receiver delivers excellent surround sound. Using the SPDIF/toslink feed from the ONN monitor only delivers stereo, no surround.
I have experimented with trying to extract dolby surround from either of the two ONN HDMI outputs with no luck.
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At this point I am reluctant to buy another flat screen monitor when this one has a decent picture. AND who knows if the next one will work as advertised unless I pay up 2x or 3x for a top line brand.
My next experiment is to purchase an outboard Roku Streaming player and feed it into the ONN flat screen HDMI input. I have two different HDMI gadgets that claim to extract 5.1 dolby.
JR