I just learned today about many centuries old astrolabe, armillary sphere, and celestial globe devices. I have very little understanding so far as to how they work, but were they made assuming the earth is a globe?

yes, since they assume the celestial and terrestrial equators as one plane and the celestial and terrestrial poles (the pillars of the Earth) as another intersecting plane. The Sun moves laterally through the constellations of the ecliptic and also at inclined angles to the poles.