Is there any way in the MIP SDK to get the last offline timestamp of a camera directly from the Camera or Hardware object?
No.
There is no direct way in the MIP SDK to retrieve a “last offline timestamp” from a camera or hardware object.
In general, XProtect VMS does not persist camera online/offline state history. Most status-related events (like Responding / Not responding) are not stored by default, so the information is simply not available afterwards.
If you change the event retention settings, it is possible to store such events going forward. In that case, you could query the Event Server and infer when a camera went offline based on stored events. To access these via the MIP SDK, I recommend starting with the Alarm and Event Viewer sample, which demonstrates how to read historical events and subscribe to new ones.