Article says the LLM is now enabled by default and there is no UI to turn it off. Is that wrong? Your link refers to Firefox 133 which is quite old by now.
Added: found the lobsters thread, https://lobste.rs/s/gntidf/firefox_forcing_llm_features
It's hard to tell from there.
Added 2: HN, I haven't looked at this yet. https://news.ycombinator.com/item?id=45858959