Ask HN: Whats the Whiteboard Solution

I'm going to develop a remote tutoring class room application which need a whiteboard.

I searched for a virtual whiteboard solution on the web, and found most of them are web based written in js. Whats more, most of them can only run on desktop, or android,or ios, and few can run on the three.

So I'm puzzled at

1) Is it much difficult to adapt the desktop version to android or ios ?

2) If I choose QT to develep desktop client, flutter( or java & swift) for mobile app, how can I integrate a js whiteboard sdk to the application ?

3) Is it an option to run the js in webview, how about its performence ?

Can anyone give me some advice ?