USB to Serial cables are for PCs, Mac, Linux etc, anything with a host port (or a USB2Go) that already has serial over USB driver software. So some do work for some versions of Android phone/tablet (but not all adaptors nor all Android versions nor all Android gadgets).
Some Kindles have internal pads or connections for TTL serial (The DXG seems to have two!), often labelled on the PCB. I never heard of a USB serial adaptor working on a Kindle eInk eReader (needs driver and host mode), more likely NDIS over USB or Serial over USB would be supported as that works even with a "dumb" client only USB port.
as that doesn't even need host mode, only
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