The PsmaesNoFootball Extension for Firefox will filter content that includes one of the following keywords and replace it with a small no-football symbol (works only partially): Click to install in Firefox It has been tested on Windows with Firefox 60.0.2
The PsmaesNoFootball Extension is licensed under the GNU General Public License v3
Download source and have fun
The PsmaesNoFootball Extension was written by eg. Contact: eg ├Ąt elisium.ch

Changelog:

0.3:

0.2:

Demo (active on the left, not active on the right):