You will need to install a user script manager extension to install this script.
put a * in front of a word for wildcard (only in the blacklist), it will find the word no matter its position in the username
whitelist: euronews (in english)
it is not case-sensitive
remember to save after any changes in the menu
you can open/close the menu either by clicking on "B" or by pressing ctrl+alt+b
right click add: you can blacklist channels by right clicking on [x] before the usernames
in any case, the [x] buttons are automatically shown when the "B" menu is open
It doesn't block channels that have the separator symbol in their names, either use a wildcard or change the separator symbol.
THE OPTION right click add MAY NOT WORK, or even in general
it probably means that youtube has changed its layout, until it changes for me too, I can't fix it