I have an LG STYLO 2 PLUS running the same version of marshmallow. I've had pleny of friends on 6.0. That formatted their sd card into internal storage( what I was planning on doing) and going about it that way. That was one of the main selling points of the marshmallow software,I'm stuck in the same boat you are. I would root my phone but when my parents went back to AZ they took my laptop by mistake. I believe your phone is rootable with kingroot,if u want to go that route