I suspect it’s the microphone. The device is with my mother-in-law across the country [assuming she still has it], so I can’t verify that for sure.

The adapter's store page lists it as compatible with every iOS device with a lightning port. Looks like that should work.

Just did this again. The last time on this Kindle I was a little brutish snapping the case back to gather and broke the replacement screen. Now that replacements screen are down to $16 I did it again and was much more careful when getting the last couple case latches seated. All good. Beats putting it in a landfill.