Ah sorry about that, I'm not sure if it's possible to do what you require, hopefully someone more knowledgeable than me can chip inThank you guys so much.
I thought Dual Audio was meant to allow you to output from any app to two speakers at the same time. The separate app sound option is just to specify where a specific app outputs to rather than to multiple devices.
The Multi sound in Sound Assistant is for when you run in split screen I think where two apps can play audio at the same time which is cool but not what I wanted.
Maybe I misunderstood the feature :-(
This you can do using "smart home" type speakers, e.g. Google Home/Nest Mini and similar that integrate with Google Home (or, I imagine, other similar apps, like Samsung SmartThings). These apps allow to create speaker groups and then play through them. But I don't think you can use any regular speakers, they should be Google Chromecast/Alexa/Sonos(?) etc. - some kind of smart speakers that can integrate with these smart home apps.I thought Dual Audio was meant to allow you to output from any app to two speakers at the same time.
Pull down the notification bar you will see two buttons device control & Media output , press media output and you can select which speakers you want sound to go from , but first all speakers / headphones & buds should be connected first