Instead of using the real camera, I would like to simulate the camera input as a static image file. I want it to work with any app, as if it was a camera. This question had been answered Use image file as camera but it doesn't work with Android 10.
The real world use case is that I will need to scan a QR code / tag from WeChat in order to use WeChat official accounts, and WeChat made it mandatory to do it via the camera. You can test it on: https://mp.weixin.qq.com/ (You will need to register an account first obviously...)