Doesn't work on Twitch for me (using Firefox). I've had some success using 'Purple Adblock', but it works by connecting to a public proxy in an ad-free country for the duration of the ad - so it has issues during peak and can get you stuck in a loop
It's been awhile since I've been on twitch, but I remember the ad would be blocked, but the player would just display "The broadcaster is currently running an ad" or something like that. Didn't see any ads though so it technically worked
It's never worked for me either, but I don't find them too intrusive in most streams.
That said if I'm watching a Warzone tournament I usually just pop out the mini player in Firefox's PIP and listen to that. They get their money and I get to keep watching.