Probably unrelated but note that GTX 580 is a Fermi card so you won't have any decent support beyond El Capitan. Limited and buggy support, if at all in Sierra/High Sierra and none afterwards. Maybe its not that unrelated... the bar I get for like 1 sec could be a graphics problem....
Ok, you are trying to use "Try Ubuntu" without install and then use linux scp command. I thought when you said scp you were referring the Dell Server Configuration Profile (SCP) feature. "Try Ubuntu" doesn't support kickstart file so that won't work for setting up SSH. Also Dell SCP...