I'm not quite sure why it started working because I'd generated another build before creating this question, but it seems to be working now. I'm pretty sure that by installing react-native-vector-icons, the problem worked itself out. I do know that in the Getting Started docs, it mentions that the library should be installed "because some components use those internally". It'd be great if react-native-paper allowed for more flexibility with customizing icon sets, but at least the issue is fixed!