Best of luck, but there are many reasons why this is not LH’s problem.
When was the cancellation relative to the flight departure? This could very well be a 100% Air Canada problem.
A strike that is not an LH strike will be considered extraordinary circumstances. And honestly, the utter mess of the AC strikes and the govt involvement etc … it’s not going to fly
Good luck - if you really want to pursue this, you will need a professional opinion and representation. There are well known lawyers out there and I could contact them for a free consultation