Some part of geothermal energy comes from gravity which could be argued is not related to fusion (even if the matter undergoing gravity was created in fusion)
Geothermal energy is derived from differences in kinetic energy between different layers of the planet (so extracting it saps kinetic energy from the planet's rotation). The energy stored in the Earth's rotation comes from the kinetic energy in the Solar nebula, which itself comes from stellar explosions in the primordial universe, which themselves were caused by fusion.