Dual Recording and Single take both of these two features are already there in Camera Assistant app but do checkout the version before searching for both of the options . For One Ui 8.5 the version should be 4.5.00.13. If its 4.0.00.6 you won't be able to find any of those options. I do recommend you to visit Sammobile website there is the latest one ui 8.5 supported camera Assistant update is available which can be updated via Google drive but make sure auto blocker feature should be turned off.
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