The only way of making it work is disabling it and enabling it for every page. It gets disabled again if you reload. It's unusable.

Doesn't work properly with Firefox 111.0.1 (64-bit). I restarted the browser after installation but had to turn the extension off and on for each new window/tab in order to swap the smart quotes. Functionally broken, sadly.

I love the intention behind it. Been waiting for such an extension for years. I hope it works!

Edit: Does not work on Wikipedia.