this is an adblock filter to hide "recommended" videos on youtube in every place in the UI where they show up, while allowing you to watch videos and browse specific channels.
you can either copy-paste the three lines in the youtube_recommended_adblock.txt
file, or you can click on the "Raw" button, and add that URL to your adblockers list of lists.
sure that you has it managed correctly? in the ublock extensions among my filters