Unfortunately I don't have the Space Age DLC, so I can't test and release the new version. You can try this:
Open geothermals.lua in notepad and find:
data.raw.planet.nauvis.map_gen_settings.autoplace_controls["geothermals"] = {}
data.raw.planet.nauvis.map_gen_settings.autoplace_settings.entity.settings["geothermals"] = {}
Replace with:
data.raw.planet["nauvis"].map_gen_settings.autoplace_controls["geothermals"] = {}
data.raw.planet["nauvis"].map_gen_settings.autoplace_settings.entity.settings["geothermals"] = {}
data.raw.planet["vulcanus"].map_gen_settings.autoplace_controls["geothermals"] = {}
data.raw.planet["vulcanus"].map_gen_settings.autoplace_settings.entity.settings["geothermals"] = {}
data.raw.planet["gleba"].map_gen_settings.autoplace_controls["geothermals"] = {}
data.raw.planet["gleba"].map_gen_settings.autoplace_settings.entity.settings["geothermals"] = {}
data.raw.planet["fulgora"].map_gen_settings.autoplace_controls["geothermals"] = {}
data.raw.planet["fulgora"].map_gen_settings.autoplace_settings.entity.settings["geothermals"] = {}
data.raw.planet["aquilo"].map_gen_settings.autoplace_controls["geothermals"] = {}
data.raw.planet["aquilo"].map_gen_settings.autoplace_settings.entity.settings["geothermals"] = {}
Open info.json in notepad and find & add DLC:
"dependencies": [
"base >= 2.0.0",
"space-age"
]