Some phones have software available to run two separated/isolated instances of the same app on a device. This may be called Dual Messenger on Samsung devices, or Parallel Apps on OnePlus devices.

Through adb we can add apps which aren’t allowed by default. No root required.

Add non-default app

First we need the user id of the Android user assigned to the secondary apps. Connect your phone, enable USB Debugging in Developer Options, and run the following. You do need adb of course.

adb shell pm list users

This will return something like the following on a OnePlus device.

	UserInfo{0:Your Name:13} running
	UserInfo{999:Parallel Apps:4000030} running

We need the number 999 or whatever you find in that location for your phone.

Now we need the .apk of the app you want. For example, you can find the .apk for Signal here.

Go to the directory of that .apk file, and run the following after replacing 999 with the id found before, and the filename of your apk.

adb install --user 999 desired_app.apk

If you get an error such as INSTALL_FAILED_VERSION_DOWNGRADE you need to add -r -d to the adb command to ignore this error.