Avram, as you mentioned yourself, there are means in halacha for applying mitzvos outside eretz yisroel. Hashem told us we’d go there, and we indeed kept the mitzvos in the midbar for 40 years before going into EY. The chinuch writes by every mitzvah, almost, that they are applicable in all areas.
Every part of the world has a shkiah, a tzeis…and yes, living in problematic areas such as Hawaii or Shanghai are discouraged bh poskim, because it isn’t clear how to keep zmanim.
But outside the earth, there’s no shkiah at all, no levana, no calendar based thereon, and no materials such as trees. Trees planted hydroponically or in an atzitz sheaino nakuv aren’t considered gidulei karka for things like schach, etc… according to most poskim.