Pour a pool of latex paint from a can you do not need anymore onto the concrete floor section you want to strip of the dried latex paint. Wait until it is dry to the touch (a few hours or overnight or even a few days). Peel off with a putty knife.
I happened on this while cleaning latex paint splatters from my living room walls onto the concrete floor and seeing how easily the relatively new splatters just peeled off and left the underlying floor free of the old, dried, otherwise super hard to remove latex. I am prepping the floor for laying groutable, peel and stick tile.