Bigtreetech upload stalled after uncommented REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER
There is a temporary solution which I have found here, on the reprap forums, Re: Upload to the board failed after LCD enabled:


  An official fix has been posted. Grab the new ultralcd.cpp from [github.com]


Apparently the sources contained a bug which was fixed later, a new version download fixed the problem.