Open the same .pptx you give the event host. Each slide’s notes become one cue card. Tap the right of the screen to go forward, the left to go back. The file is read on this tablet and never uploaded.
Tip: cue chains like 40 data points→6 charts work well. Type -> in your notes and it shows as an arrow. Add [2m] to give a slide its own time, and Target: 20 min on the first slide for the whole talk. The timer starts when you first move forward, or tap it to start sooner.