Yesterday I tried to activate the Accessibility Services of Android on OPO to get some apps to work which enable a software navigation bar for having a back button for apps with a lack of such. After having activated this service the screen went black for my apps. So now it's not possible to see my installed app UI and also the android settings UI can't be made visible to reset that behavior. Superficial search in the code of Anbox let me assume, that there is intended only one Layer for the UI. Maybe that's ok for the PC desktop solution but for the smartphone solution too?
For now I only found a workaround for step back to a former activity of top app on the stack with 'adb shell input keyevent 4'. Are there better solutions for that?
For another try I now installed an app with f-droid for a navigation bar and enabled it. Even if the softkeys, are not visible it seems that they work anyway. When I swipe up from the lower edge of the screen as if I would make visible the navigation bar and tap on the screen where the back button should be, the app steps back. Can someone confirm that on another phone?
In SailfishOS the Android apps are opened with a return button underneath. Is something like this possible in Ubuntu Touch? Even the android settings app delivered with anbox need a return button for some setting menus.