It doesn't skip ads, but mutes the sound, but the actual track doesn't play. The playlist simply stops at the ad.

doesnt work anymore, spotify detects it and shows a banner about refreshing the page

Use uBlock Origin instead:
https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

Es una mierd@, solo mutea el audio cada segundo, imposible de usar.

un asco total es una broma de mal gusto