In this answer to Why do the Borg have physical computer interfaces?, the poster states:
As mentioned by MarvelX42, when assimilating a ship that uses screens, it makes sense to just keep using those screens rather than to re-program the whole ship to bypass them. This is especially compelling since we see "Borg consoles" much more often on assimilated ships, like the Enterprise-E, than on native Borg constructs, like the Cubes, where Drones are more commonly locked into their docking stations.
What is the final or end state of a starship of non-Borg origin that has been assimilated by the Borg? In First Contact, we see an attempt to assimilate the Enterprise-E in which the Borg interface their own systems with the Enterprise's existing systems, but the attempt is stopped before it is completed and so we do not find out what would have happened if it had been completed.
When a ship has been fully assimilated, what happens to it?
- Is it converted into a Cube or other Borg ship design (e.g. existing Cubes might have remnants of whatever ship they were originally deep down somewhere in their cores, or they might become Cubes of Theseus)?
- Does it become a Borg-mod version of whatever ship it was originally, with many of its original quirks preserved (e.g. somewhere out there in Borg space may be Borgified Cardassian Galor-class cruisers, Klingon Birds-of-Prey, etc., assigned to less-important patrols and missions that do not require the full might of a Cube)?
- Is it flown to the nearest Borg base and disassembled for parts or materials?
Is this ever explained at any level of canon, including novels?