Interesting. I have heard of Flex but I don't know much about it.
Some of these examples don't work properly in Ruffle. At least the Rich Text is buggy, and mouse scrolling doesn't work. I haven't tested them all.
I have reported the issues to the Ruffle team, so they should be fixed eventually.
It's interesting to see that most of this stuff exists in HTML5 now. But not all of it!