Requirements
  Create Bootable Ubuntu USB
  - Open the dash and search for Startup Disk Creator.
- Select the Startup Disk Creator to launch the app.  
- Click Other to choose the downloaded ISO file.
- Select the file and click Open.  
- Select the USB stick in the bottom box and click Make Startup Disk.  
- That’s it! When the process completes, you’ll be ready to restart your computer and begin installing Ubuntu.
Fix gfxboot.c32 not a com32r image
 
  - Hit TAB
- Then you will see a set of options (live, live install, etc).
- Now type liveand pressENTRER.
Reference
             
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