I can't seem to get the iPad to recognize any device I plug into either of the adapters. Errors say "device not supported" or "the volume is not recognizable". Do I need a driver or app to make these work?

What "device" are you trying to plug in?

Some USB keyboards will pop up that "unsupported" message, but you can dismiss it and it will keep working. But that message will pop up every few minutes.

And the "volume not recognizable" sounds like you're trying to plug in an external harddrive. That definitely won't work.