You are just trying to do something that nobody cares about making work on smartphones, and so you are "on your own".
Trying to do userland USB in an Android app to talk to a UVC webcam connected through USB OTG is not something even a niche of apps care for, and the native camera framework definitely doesn't care about because if it was trying to workaround the UVC spec Android phone cameras would have never left the original Gameboy camera age.
So with no native support for your use case, you are now having to wrangle the pretty shitty libusb and the even more terrible libuvc in working within the confines of an Android app. And to the credit of Android, this is possible! People have made it work! People with in depth knowledge of how the parts fit together, that is, and so GPT won't be of any help.
Trying to do userland USB in an Android app to talk to a UVC webcam connected through USB OTG is not something even a niche of apps care for, and the native camera framework definitely doesn't care about because if it was trying to workaround the UVC spec Android phone cameras would have never left the original Gameboy camera age.
So with no native support for your use case, you are now having to wrangle the pretty shitty libusb and the even more terrible libuvc in working within the confines of an Android app. And to the credit of Android, this is possible! People have made it work! People with in depth knowledge of how the parts fit together, that is, and so GPT won't be of any help.