The most current public listings I found say Lost is available on Disney Plus and Hulu , but not for free right now in Canada, and ITVX has it in the UK.

Free options

There does not appear to be a legal free streaming option available at the moment.

Legal ways to watch

  • Disney Plus : streaming option.
  • Hulu : streaming option with all 6 seasons listed.
  • ITVX : available in the UK.

Free-but-not-streaming

A library DVD borrow is the safest free option if you want to avoid paid streaming, and older forum posts also mention network and ad-supported availability, though those are outdated and not reliable for today.

If you want, I can narrow it down by country and format it as a simple watch guide.