This looks very nice for teachers. But having to install the extension is the limiting factor that doesn't make it practical for mass use.
The demo is on the homepage, fyi: https://plopdown.video/
The demo is on the homepage, fyi: https://plopdown.video/
You should be able to store a track pretty much anywhere (github gists, pastebin) then associate them with a video and share the setup via that link. If you don't have the extension installed, it would show a preview and will prompt you to install the extension before proceeding.
However, it doesn't overlay any annotations over the video like plopdown does (which is a great feature!), only on the side of the video.