I've been pondering this. I think either no note or one explaining reasons but brief. I thought maybe imagine what people left behind would ask. But then it seems all they ask is why? I was going to say something to the people who walked away from me but what would that achieve, and pretty nasty to do that so I won't do it. It's a very individual thing. I'm beginning to come round to not leaving a note. Not sure if I'll get rid of my journal before I go. It explains my tortured head but names people. Not a great answer for you, sorry
If there are incorrect assumptions about you that people might make, yes, personally I would address them in a note. I did that already in a seemingly innocuous Facebook post