I don't think strikebreaking is illegal by law in Sweden (but long time I lived in Sweden and was more involved, maybe I remember things wrong or things have changed). But definitely wildly frowned upon, so if the article I linked before is true, then there will be solidarity strikes for sure.

I think threatening with layoffs if striking is also not illegal? But historically, with the Scandinavian union model, you’re in for a ride. E.g. with union-supported class actions from fired employees.