I believe that the existence of god (or another deity) is unknownable
If you mean it is inherently unknowable, rather than "not knowable given our current level of understanding" or something like that, then this is usually called "strong" or "hard" agnosticism (contrast "weak" or "soft" agnosticism, which usually means that a deity's existence is not known to you, based on current evidence). Strong agnosticism is an epistemic claim, that is, a claim about how knowledge works and what we can or cannot learn, while weak agnosticism is more of a claim about the evidence as it currently stands. Taken to its logical conclusion, strong agnosticism should be an a priori claim, meaning you can't convince such an agnostic of the existence of a deity even if (say) God walks right up to them and does a miracle before their very eyes (because, for example, it might be caused by a hallucination, a trick, some previously undocumented law of nature, etc.). However, this line of reasoning ultimately runs into many of the same problems as solipsism, unless you adopt a non-cognitivist position (i.e. claim that "god" and "deity" are ill-defined terms, for example because you don't think there is a logically coherent distinction between the natural and the supernatural - if the laws of physics may be broken, then they are not the true laws). This would make you a theological non-cognitivist instead of an agnostic, but it does not seem to match up with what you have described in the question.