Flash is not installed by Ubuntu Restricted Extras, therefore making this script redundant.

Open up the Terminal on the desired system. Download and run the script using the following command:

wget https://raw.githubusercontent.com/quidsup/flashless-extras/master/flashless.sh && bash flashless.sh

After you have run the script, you may remove it using the following command:

rm flashless.sh

This work is licensed under the GPLv3 license. You may read it at any time here.