When running a job on the Grid (backend = Dirac()), the output data can be stored on a Grid Storage Element (SE) instead of the lxplus AFS account. The access to the files is however a bit different than on lxplus.

go to your home directory on lxplus open the .gangarc file modify the following line (line 313 in standard .gangarc file (to get a standard one do 'ganga -g')):

#outputsandbox_types = ['NTupleSvc', 'HistogramPersistencySvc', 'MicroDSTStream']

here are 3 services in the list: NTupleSvc produces .root files, HistogramPersistencySvc produces histograms, MicroDSTStream produces .dst files.
Outputsandbox means, the output files of these services end up in your sandbox folder on lxplus.
If you want the output files NOT to end up on lxplus, but somewhere else, remove the service from the list.
For example if you don't want your .root files on lxplus uncomment the line and remove 'NTupleSvc':

outputsandbox_types = ['HistogramPersistencySvc', 'MicroDSTStream']

save the .gangarc file
restart Ganga

in Ganga choose the outputdata option for your job and not outputsandbox, i.e.:

ntuple = "filename.root"
j.outputdata = [ntuple]