You want one screen. The big one. Clamshell needs a charger. Brightness to zero doesn't disable it. Apps still open there. OneDisplay fixes this with one click. Click the menu bar icon, MacBook display turns off, only your external monitor stays on. Click again to bring it back. No setup. No background process. No configuration. Works on Apple Silicon (M1, M2, M3, M4) and macOS Ventura or later. $9. One-time. Yours forever. Not happy? Full refund, no questions asked.