Short version: video posting still works, but you have to be quick about it. Discourse has a bug where it’ll give you an error once the links have been converted to the embedded version.
The workaround is to write your post, but don’t put in the YouTube links yet. When you’re ready to submit, paste the links and immediately hit the reply button.
Also, your existing links won’t work now that Discourse has seen them. But you can tweak them slightly to get them going by appending a “&1”, “&2”, etc. to the end. Working versions:
