This makes YouTube an infinitely better user experience! I really appreciate the lack of visual clutter all the loud thumbnails cause especially. It does make my subscriptions & home page load a little more slowly, but that's well worth it in my opinion.

For some channels I'm subscribed to (like crochet/craft channels), I found I missed the thumbnails because those show the finished craft product, thankfully it was easy to whitelist those.

I did also change the default thumbnail replacement from "random" to "auto-generated by YouTube", which led to less awkward half-blink faces in my feed.

Once activated, the extension immediately worked on all my devices where I'm logged in to Firefox, and I was able to re-use the activation code on a shared family device where I am not logged in on my Firefox account. Overall, a great experience and well worth the 1 euro.