This issue has been addressed in this thread.
You won’t be able to do it from the hamburger menu on your phone since the screen keeps reloading, but you can enter any JG Community url in your Android/iOS browser and change the mobile_view parameter from ‘?mobile_view=1’ to ‘?mobile_view=0’.
This forces mobile view off:
https://community.justinguitar.com/?mobile_view=0
And this would force mobile view back on: