[Solved] Guest permissions: Topics not visible
I finally solved the problem and it's really stupid...
I had "looped" the permissions settings too much and unchecked certain boxes that it seemed logical to me to uncheck, such as "Can start a topic" and "can subscribe" but in fact they have to be left checked.
It was by persevering and thanks to an answer from @robert that I finally found it. These boxes must be checked!