Lubuntu 18.04 Unreadable screens when joining dual monitors
  
 
     
     
             
                 
 
 
         
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 I installed Lubuntu-core (via 18.04 mini.iso) on a USB flash drive and it works great with one monitor.  When I plug in a second monitor on the same card and set the displays to be joined rather than mirrored, the screens become unreadable. Mirrored works fine.  I tried adjusting the resolution and refresh rate for both, but couldn't find a combination that worked.   lspci -nn | grep -E 'VGA|Display' shows  01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, INC. [AMD/ATI] RV370 [Radeon X300] [1002:5b60]  01:00.1 Display controller [0380]: Advanced Micro Devices, INC. [AMD/ATI] RV370 [Radeon X300 SE] [1002:5b70]   I have used this card before with Lubuntu with not problem, but that was when it was installed on a hard drive, not USB flash drive.   Does anyone have any suggestions or advic...