So far I tried:
Lenovo Super Camera: Allows you to set the iso, but simply ignores the value set
Camera FV-5: Same as above
Focal: Can't find an option to set ISO
ProCapture: No manual ISO control (Will be in a next release, but device miight not be supported)
Pudding Camera; No manual ISO control
Camera360: "Your device does not support this" message
Camera ZoomFX: No manual ISO control
So I'm afraid it will be impossible for third party apps to control the ISO values. Which wouldn't be too bad if I could access the setting more directly in the native camera app.
Anyone with tips or tricks for this?