So, correct me if I’m wrong, but wouldn’t a 500c magma lake make the rocks nearby hotter than 20c? I’ve had the geothermal available for a while, but I have to be IN lava for it to do anything, which I can’t do for more than a few seconds right now, so it would make sense to have areas near the lava be warm enough to activate the geothermal, even if it’s only at half capacity or something. Not that I really understand what it’s for, as you can’t have active modules when you’re underground and the boiler tends to be good enough to deal with minor hub production that doesn’t require modules.
Or increase the temperature T3 of the yellow hull to withstand 500°c.