===== Shared (white) board =====
  * https://awwapp.com free version has some limitations, among others, no save, just export to PDF with watermark and no multipage, and a bit disturbing add banner at the bottom
    * drawing, typing, moving objects etc, very comfortable
    * pointing visible - users may point on objects, the other can see
  * BigBlueButton offers shared board. You can either draw to the uploaded PDF presentation or used the default one - go to next page. All-drawing can be anabled by using the menu on right.
  * https://whiteboardfox.com/ is free by default, very simplistic, but perhaps good enough for start
  * https://miro.com/online-whiteboard/ 3 active boards for free
  * overview https://zapier.com/blog/best-online-whiteboard/