As far as I've heard, SAG and WGA are not asking people to cancel their subscriptions. In fact, mass cancellations could hurt their position in the strike, since the streaming services will use the "volatility" of the subscription model and lowered revenue from boycotts to support paying people less. Other than not crossing the picket line (if you're in the industry), being vocally in support of the unions is pretty much all we can do at this moment if you're not in LA. There are some relief charities that need funding if you want to donate or signal boost those.