I’m not encountering this in 8.0.6 while using Chrome 78.0.3904.70, but there shouldn’t be significan differences between the Ignition version or the Chrome version - at least nothing that would result in the Menu Tree not displaying.
Could you provide some screenshots (at least for the desktop Chrome)? I’ll continue to investigate the Android claim.
Note: If your popup is large enough to display even partially off the viewport, then the popup will be draggable whether or not you configure it to not be draggable.
I can reproduce this on a different Ignition 8.0.6 RC1 with Chrome and Windows 10. The key is to set the FlexContainer with the MenuTree to Column mode. In Row mode the MenuTree is visible.
The menu also becomes visible as soon as the browser window is resized.