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Depends on what you mean by usable. Many of the old plate cameras and lenses are usable these days with modern large format films, papers, and traditional processes. As you move into the roll films it becomes more hit and miss as some of the formats are no longer used. As cameras gain electric parts finding batteries can be problematic as the type of batteries used in some of them are no longer made (like literally the chemistry for it not just the size and shape). For some of these missing batteries modern equivalents can be mickey moused together. When you get to cameras with specialized film cartridges it becomes harder to impractical to uses them as you have to custom make them.
Of course you can use pre-photography camera obscuras with sheet film or paper. Camera obscuras became popular in the 17th century and with very minor work a lot them could be used to shoot with. Optics for camera obscuras show up back in the 15th century? maybe the 14th? I can't remember when without checking. Those could be usable as well. Before optics show up camera obscuras worked just like a modern pinhole camera does. Camera obscuras show up in written works 500 BCE... so 500 BCE would be the oldest officially described camera you could theoretically find to use. The camera obscura effect was probably known before then but it would be difficult to prove that what you are using is a pre-500bce camera obscura.
