Do all borg ships start off as another alien vessle that the borg assimilate, then keep adding on to it like in ENT. Or do they manufacture most of or any of them?
The transport in Enterprise was heavily assimilated by the end of the episode, but did not resemble a a cube to begin with.
The Borg can find numerous inefficient aspects in a human made ship for example and turn those into something that is in fact efficient to them, which is why they were able to do to it what they did.
Was it ever explained in any way what the ship in TNG's Descent was that the Borg had or was it itself just another Borg vessel even though the Borg onboard were not part of the Collective?
I don't think there's a definitive canon answer for this
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