The current king of open-source Dreamcast emulation is (available via RetroArch). Flycast is excellent for power users who want tweaks like widescreen hacks or online play, but for simplicity and speed on a phone, Redream remains the best choice.
The original NullDC Android project is dead. While the APK exists on GitHub, it is a time capsule for old phones (Android 6-8). If you have a modern flagship like a Samsung Galaxy S23 or Google Pixel 7, the legacy APK will likely refuse to run. nulldc android apk download
Active development ensures best compatibility for Dreamcast, NAOMI, and Atomiswave. It is frequently updated with new features, including online Netplay. The current king of open-source Dreamcast emulation is