Drawing on roll20 with an iPad via Duet Display - anyone tried this?

I recently got a new iPad. I’d love to be able to sketch quick roll20 maps on it during a session. The official iPad app seems to be totally broken these days (I believe it’s being rewritten?) and doesn’t seem to have ever allowed this anyway. Similarly, logging into roll20 directly via mobile Safari doesn’t seem to work well.  That leaves me with the idea of slaving the iPad to my (Windows) desktop PC via Duet Display (or similar “use your IPad as a monitor” app) and using it as a makeshift drawing tablet. Before I buy Duet Display just to discover it doesn’t work - has anyone tried this out? Is this a good / bad idea?

Have you tried Chrome or Firefox? Safari browser is not supported.

I am aware Safari (desktop or mobile) isn't supported by roll20. That's fair enough. However, Safari is all you have on iPad. The iOS versions of Chrome and Firefox are merely different UI wrappers around the same Safari-derived rendering engine and JavaScript runtime. It's an app store rules thing. Specifically : "2.5.6 Apps that browse the web must use the appropriate WebKit framework and WebKit Javascript." WebKit is the guts of Safari. From a website compatibility point of view, all iOS browsers are equivalent. 

That's interesting, but the wrapper might make the difference.

Bit of a delay, there, while my iPad failed, was returned, and (eventually) replaced. I can now answer my own question for any future readers of the thread and confirm that: Mobile Safari on the iPad does not support Apple Pencil (or finger-based) drawing using the Freehand tool in roll20. Indeed, there are numerous problems with the site in Safari, which I will not enumerate here as I know it's not supported. Chrome for iPad behaves identically to Safari. As I wrote above, this is not surprising, as they share a rendering engine and JavaScript implementation. From roll20's perspective, they are more or less the same browser. Duet Display Pro for iPad (connected to, and driven by, a Windows PC) does not allow Freehand drawing either, with either Apple Pencil or finger. You can drag a Chrome (v81.0.4044.138) window over to the iPad's screen fine, and you can select tools from roll20's toolbar with the Apple Pencil, but touching the screen with either Pencil or finger doesn't cause roll20 to map any drawing events. So you cannot do freehand sketching. Firefox (v76.0.1) behaves the same way as Chrome does. Apple Pencil can be used within the roll20 UI but it can't be used to draw anything. Frustrating, but not exactly surprising. I haven't yet tried Apple's Sidecar implementation. That doesn't work well for me as my MacBook can't drive my main monitor and the iPad at full resolution at the same time, so it's not a setup I would use anyway. However I may try it out of interest. If I get around to it I'll post results here.