Google camera can be installed on Asus m1 max pro after enabling camera2api. The below steps are assuming you have a Mac machine with adb and fastboot tools and developer option and usb debugging is enabled on your Asus m1 max pro.
adb reboot bootloader
- Enable camera2api
fastboot oem enable_camera_hal3 true
- Reboot device
- Install Manual camera compatibility app and check if your device now support manual camera settings introduced in camera2api.
- Install Google camera app from site https://www.celsoazevedo.com/files/android/google-camera/