- Download ``script.pac`` to ``/home/user/script.pac ``
- Go to FF network settings and select 'Automatic proxy configuration URL'
- Enter ``file:///home/user/script.pac``
- Enjoy

Note: If you're using SOCKS v5 you might want to also select 'Proxy DNS when using SOCKS v5'

Tested on 116.0.2 (64 bit) Arch Linux