There are multiple ways to do this. This is a way I’m having success with. If you simply harp on it, the hex cut in the link can strip right out, and if you put an impact on it, the ball will just spin. Sometimes you can hold the ball with vice grips while impacting the nut off.
I found it was easier with this car to slice the links with an angle grinder and then remove the bar all together. I was doing links and bushings either way. (2009 Subaru Forester).
Steps:
Heat
Rust Penetrant
Break flange nut loose from surface (important)
Turn with wrench and hex bit/allen
Rejoice