I am not getting any user interface to work with on dupeguru, fslint

FSlint is in the default Ubuntu repositories for all currently supported versions of Ubuntu. To install it open the terminal and type:

sudo apt install fslint

The link for installing dupeGuru Music Edition (the more full featured version of dupeGuru) in Ubuntu 14.04 is found in the answer by Li Lo to How can I find duplicate songs?. There is also information about other alternative applications for getting rid of duplicate files in the other answers to the same question. If you are finding it difficult to choose which application to install, I recommend that you select an application for getting rid of duplicate files from the Ubuntu Software Center.

If you are having any difficulty getting the interface to work properly with any of these programs, you should check if all of your drives are mounted at startup.