I seem to remember from the other site that on-line teaching was relatively new, and you were trying to find out more about it - my memory is vague. Since I've had regular lessons on-line for years, I had a look at your advice.
You say that PC's cannot be used. I only got a laptop recently and used a PC. A webcam - many use Logitech - microphone, possibly with a mixer. If the student has a digital piano then sound can be transmitted straight to you via cable.
Laptop and tablet are other choices, but PC is also a choice.
You list Skype, Google Hangouts, Facetime, Zoom and Messenger
You say Skype is "preferred" because of screen sharing. That can also be done on Zoom. Is Google Hangouts still around? I don't know if you read the posts on the topic in this forum. Most people are selecting Zoom. The sound quality on Skype has deteriorated over the past few years. If you are advising teachers here that Skype is preferable, then I can't agree.
The organizational info on lessons themselves seems decent, although it seems to be geared toward your own staff, rather than the colleagues you are addressing here.
Back to this:
This device can't move TO the keyboard, so if this is not near, we must rule it out.
A webcam can move to the keyboard, so there is no reason to rule this out. I'd also say that a camera with a decent stand gives more possibilities than a laptop, which is rather big and clunky by comparison.