Personally, I had this problem when I tried to test my app through my iPhone 8 Plus instead of the simulation. What Xcode is asking you is to select a development team to be able to sign the app and install it on your device.
Follow these steps to resolve the issue.
1 - Go to Xcode Preferences and add your Apple ID account into Xcode
2 - Make sure that you click Manage Certificates and click the + on the bottom left and click Apple Development
3 - Click your Apps Project on the Project Navigator then Click on "Signing & Capabilities"
4 - Finally click on Team to select your team. It should be your (Personal Team)
MisaelDev1
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