As a rule, if you connect the front camera of the smartphone, you cannot photograph or film at the same time with the rear camera. But with the MixCam app you can do it, which can become a useful application for, for example, making vlogs or videos of live reactions.
The application also has a group photo mode to never be left out of a memory. If you take an image of several people, you can therefore include yourself.
Note, however, that the app only works on the following Apple models with iOS 13: XR, XS, XS Max and iPhone 11.
MixCam is free and available at App Store but the pictures are watermarked. You can choose the premium version that, among the many advantages, removes the watermark from the photos and videos.