It's very bare-bones, but the solution that works most reliably for me is still https://awwapp.com (has been around for ages)
That still leaves a lot of room for improvement. I'd love to see something that has a native iOS app with great Pencil support, as well as clients for other platforms (anything that people tend to use with a pen, like MS Surface), and also a web-app as a fall-back, at least read-only. Low-latency is a must. There are a bunch of solutions I've tried, but most take something like 20 seconds for things to shop up on all the clients (or longer, like a shared One-Note notebook). That just doesn't work for a video conference.
That still leaves a lot of room for improvement. I'd love to see something that has a native iOS app with great Pencil support, as well as clients for other platforms (anything that people tend to use with a pen, like MS Surface), and also a web-app as a fall-back, at least read-only. Low-latency is a must. There are a bunch of solutions I've tried, but most take something like 20 seconds for things to shop up on all the clients (or longer, like a shared One-Note notebook). That just doesn't work for a video conference.