Xposed modules (can even be targetted at specific apps in a root-less way using Taichi), patching system libraries with smalipatcher to disable the "secure flag" system wide or root screen capture tools like scrcpy.

With another device that takes pictures

I’m glad I’m privileged enough to have multiple devices with cameras

Its a low bar, but I was told to check my privilege and I do love doing that now

One trick is to use scrcpy then make the screenshot with your computer instead