Ok fair. Two 120V rails in series would supply 240V but I think the dangerous part comes from the ‘also’ and that’s where an electrician would come in and turn this from ‘just a breaker’ to rewiring your house.
you will also need to replace your receptacle
True.
You will also need to upgrade to 12/2
True.
I just don’t think it’s safe to say ‘yes just add a 240V breaker and plug it in’ which appears the OP may be at their with level of understanding.
Be the change you wish to see in the world. Also, fuck spez.