Normal users will be fine if they will see two big squares side by side as an installation step: „with AI“ and „without AI“, where the former will just install and enable the plugin. Explicit choice is better than opt-out, and it’s not going to be something people frequently change their mind about, so another switch can be buried in settings.

Firefox has <5% of browser share, no one is a normal user of firefox.

Who is a "normal" user.

Normal users install Chrome.