[MC5C]

Heat press is indeed one way, but controversial in some circles (Like the internet... :0 ). It depends on heat and pressure to slip the glue joint between the fretboard and the neck (if the glue used can be "slipped") or simply uses heat to facilitate bending the neck until it's straight again. Reports vary between "it worked for 20 years for me" to "it lasted 6 months".

Another way to deal with it (not one I particularly favor) is to de-fret, plane/sand the fretboard straight (not the neck) and re-fret. Thins the fretboard at both ends, which may or may not be a serious issue, but has the advantage of leaving the neck in the place it's decided it wants to be. Might have visual problems, or structural problems, if too much needs to come off the fretboard.

Most drastic, and probably best solution mechanically, would be to remove the fretboard, heat/press the neck straight, install a truss rod to stiffen the neck and hold it in place (could be an adjustable truss rod, or an aluminium/carbon fiber insert) and replace the fretboard. If it was mine, I'd try the first method first, heat/bend/slip the neck into place and see what happens. You lose nothing by trying that way first (except a couple of bucks).