Yes, my kid has ADHD. The browser add-on does the job at slowing down the impulse of going to YouTube (and a few online gaming sites) during homework hours.

I've deployed the same one for me, but setup for Reddit during work hours.

Both of us know how to get around the add-on. It's not particularly hard. But since Firefox is the primary browser for both of us, it does the trick.

For those that don't want to build their own addon, Cold turkey Blocker works quite well. It supports multiple browsers and can block apps too.

I'm not affiliated with them, but it has helped me when I really need to focus.

https://getcoldturkey.com/