Not even a whole sock?

What are YOU washig?

Same, I was wondering how bad mine was after I finally found where it was. Barely anything 🤷

my guess is, that those are combined dryer/washer machines. in my old place we had dedicated dryers, those could build up a felt just after one load.

currently we have a washer (non drying) and the filter is a small tube shaped thing under the main door. it never builds up much, except someone forgot some paper in their jeans...