The Onn projector is actually just a projector with a Roku Streaming Stick in the HDMI port, powered by the USB port, isn't is?
If that's the case, then Walmart (Onn is their brand) would be best for hooking up a sound bar.
However, giving it a shot, since there is a second HDMI port, does connecting the sound bar to that port not work? Alternately, the Aux output might be an option.
DBDukes
Roku Community Streaming Expert
Note: I am not a Roku employee.
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