"Natural geothermal processes" is no more protected from an argument for intelligent design than anything else. Your general position therefore becomes unintelligible and trivial.
If a natural geothermal process produces a strand of RNA, for example, then that counts as a reason to think RNA is not the product of design. It is still possible that RNA is designed but mere possibilities do not count as actual evidence and so are excluded when we try to determine whether the preponderance of the evidence says RNA is designed or not.