Not sure exactly what you want to do but, have you thought about something else?
Run a cloud of devices where subscribers can volunteer to do a visual check if a UI behaves well? These subscribers volunteer for receiving a layout in a B4A app. on their device.
So devs. can deploy to a bunch of devices (maybe through push notifications) and the users just say: looks ok to me or does not look ok.
You wouldn't need to have and run all these devices because volunteers would have them. You can never own all the devices that users have, impossible.
Every developer could actually get volunteers for you through their app by supporting the system. This is also a great way to advertise new apps, users get early preview screenshots and rate them.
So basically the cloud of devices is created among users and not run by you. This is also a way for developers to get to users.
Maybe you can even record which people subscribe through which app.
Cheers,