https://www.cnet.com/news/huawei-p30-pro-bonkers-periscope-camera-shown-in-youtube-teardown-video/

The zoom camera is particularly interesting because it has 5x optical zoom and 50x digital zoom. As opposed to having the lens stick out of the back of the phone, Huawei built it into the phone sideways -- with a periscope-style mirror to reflect light into the sensor. Fast-forward to 6 minutes in to see the relevant section of the video.

In the video, Zack Nelson not only dissects the periscope camera module to reveal the lens and magnifier, but he shows how the in-screen fingerprint readers works. When the unit it is removed from the phone, there's a small clear circle in the display where your finger would normally go.