I personally am against it. I think that a future socialist Spain would be stronger if it was unified, and division would threaten that. I also don’t think the arguments for seperation are that strong and the pro-independence movement is not just left wingers. I think like half of the movement are liberals, like Puigdemont.
But I’m not that well read in this topic so if you think otherwise I’m willing to listen
In general I think it weakens a bourgeois state and that is good. A independent breakaway state has better prospects for socialist governance and a nation that has had a secession would suffer a legitimacy set back that could make a successful socialist revolution more possible.
It also leaves it extremely vulnerable when surrounded by capitalist states with more money, weapons and power. Also to sanctions/embargo.