When building your android app locally, by default you build all the 4 Application Binary Interfaces (ABIs) : armeabi-v7a, arm64-v8a, x86 & x86_64.
However, you probably don't need to build all of them if you're building locally and testing your emulator or on a physical device.
This should reduce your native build time by a ~75% factor.
npx react-native run-android --active-arch-only