We can embed visuals of a sheet very easily, with:
const vis = await qlikApp.visualization.get('<visual_id>');
vis.show('<visual_container>'); // Renders visual in the given HTML container
But, I could not find any such API for embedding Qlik sheet.
In the docs, I only found embedding sheet by copy pasting iframe
I don't think its possible to embed the whole sheet using the Visualization API. This API is targeting specifically visualizations (charts, tables etc.)
The only option I'm aware of is the iFrame (aka Single Interation API)
Seems that someone tried to "emulate" Qlik Sense sheet here. But it looks like this will display only the sheet objects (no selections bar for example).