I've never seen an ad on Twitch with uBlock origin installed. If this technology can't bypass ad blockers, why is there a difference?
You may be ad-free for another reason such as a grandfathered twitch prime that will expire when it next renews, twitch turbo, or a subscription to a channel that opts-in to the ad-free sub benefit. You might also just be in a region or demographic where ads aren't being bought, so you wouldn't get any then.
Now, whenever I get an ad, I immediately close twitch and find something on YT/Mixer to watch. I'm training their algorithms to leave me alone.
I get ads when I use Twitch, with the same account, on a stock installation of Chrome (which I use as my backup browser for when I don’t want to figure out which extension is breaking a website). So it’s not related to my account, location, etc.