Add a Browser source (OBS: Browser; Ecamm Live: Overlays, Browser; vMix: Add Input, Web Browser) with this address, sized 1920 × 1080. For a phone stream use 1080 × 1920; it switches by itself.
In OBS, untick "Shutdown source when not visible". Nothing shows until you press Take.
Scan this with the phone that will run the lower thirds. It opens this same panel, already connected.
This link can put words on your stream. Share it only with the person running lower thirds.
Docks, Custom Browser Docks, name it "Lower Thirds", paste this panel's address. The panel and the overlay then talk inside OBS even without internet.
Enter takes the selected lower third. Esc clears. Right arrow takes the next one. Up and down move through the rundown.
A new link stops the old one working. Then paste the new overlay address into your streaming app.
Lower Thirds