Question I'm confused about regarding heat death.

Let's say right now, Earth somehow escapes the suns orbit, escapes the Milky Way, and escapes our galactic cluster. We become a fully rogue planet hurdling off into the void forever.

After all the stars burn out and all the black holes dissipate, what would become of Earth? Does heat death mean the particles holding Earth together somehow break up and the rocky planet is no more or it's just a cold dead husk drifting through pure blackness for the rest of all time? I don't really know what proton decay implies.