I'm not sure this will do the trick, but Sidecar works for me. You need an appropriate computer and iPad, of course.
Once you turn on Sidecar, you can drag the Wolfram Documentation window to the iPad. You can use the computer's keyboard to enter stuff, and interact with the mouse. You can also use the keyboard on the iPad -- an icon on the right (by default) brings it up. I haven't tried all the different ways of interacting.
In most respects, it works just like a second monitor, except you can use Apple Pencil to interact with the iPad directly. The scroll bars appear so you can use the pencil to drag them. all the controls work with the Apple Pencil, so it is really nifty.
Right now, there is no way to execute the shift-enter combination using the Apple Pencil. Since Wolfram already has a mechanism to implement the numeric keypad enter key with the extended keyboard, this could be implemented, I think.
If that were possible, then the combination of Sidecar, the iPad and the Apple Pencil would work an allow the content or window on the iPad to be used without recourse to the Mac.
Based on this experience, I would say that a 'native' Mathematica for iPad would work just fine, using the Apple Pencil and the keyboard, without needing to use the overly large keyboard I see sometimes.
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The Wolfram Player has the Documentation center already implemented. The downside is that the examples (for Manipulate at least) are implemented as short videos, rather than being live. If that meets your needs, then Wolfram has already provided a free solution.
As a 'passive' reader, this would be sufficient. However, now that I see what can be done with Sidecar and the Apple Pencil, it is really barebones. With Sidecar, I can still copy and paste examples, and do everything I can in Mathematica, and still use the pencil to manipulate stuff without using the computer keyboard.