You just have to remember to proofread carefully before posting and make sure you’ve said everything you need to say, because there ain’t no going back!
It’s possible, but I recall other posters being able to post YouTube videos with the standard youtube.com link. It seems to be sensitive to your precise OS+browser configuration. Most of us can manage to post most of the time with the youtu.be link and the appended slash, but even that fails to work some of the time, apparently at random. It really is a legitimate bug.
Good to hear!
As noted above, the workaround tricks don’t always work. It’s intermittent.
I’ve found I can only post one at a time and have them playable. I get the error if I try to do more than one in a post. Which is a problem if I have a few videos to share in a thread and don’t want to run afoul of the “no spamming” restriction by board software.
And I have to use the youtu.be trick or I can’t even do one.
[Snarky tangent]
I remember the HORROR when the shift to Discourse1 was proposed because We don’t want avatars and pictures and :gasp: videos on our pristine text only site. WORDS should be enough dangit!
And look at us now… 
1Not that Discourse is a phenomenal MB software, as evidenced by this thread and many others. It’s just that apart from a few holdouts we seem to have adopted well enough and the sky didn’t fall down.
Insert pressed like button here.
I posted a youtube link. Tried editing and it wouldn’t let me save.
I enter text “Link” and then pasted the youtube link
That worked. It does require people to click the link to load youtube.
Heck, I can’t even post a link to a .mp3 without getting this error. I had to put a space at the beginning to be able to post it. Using that method, I can edit it afterward.
As of today, this is also broken. I can’t post a single video with a preview using any method. It’s 100% broken.
All I can post are bare links, and someone has to click on it and go to YouTube to watch it.
I really think that this is a problem with the board’s configuration, but without a real administrator to make changes we’re stuck with what we have I guess.
No, it’s just wildly inconsistent, as always.
It used to be.
Now I can’t post anything from any browser using any method.
I guess maybe it’s just not consistent from user to user. But it’s 100% broke for me now.
It’s been a few days since I tried but for me it seemed to run in spurts; total failure for a couple days, then intermittent success for a couple days, then …
Heck, for all we know there’s something subtly different in how YouTube responds to Discourse’s queries to build the preview and what’s actually wrong / different is at YouTube, not at your browser.
My current theory: it works if you do everything quickly. You know how it takes a second or two for the preview window to convert the raw link into the actual embedded window? I think it works if you hit the “reply” button before that conversion happens.
The ideas about using a “youtu.be” link don’t work, but they seem like they work because the user is pasting a new link, and sometimes they manage to submit it before the system has parsed it (causing the failure).
Youtube:
“Sorry, an error occured…”
Yewtube:
That’s not my experience. The preview window has always already been constructed when I post. What I find is that the YouTube URL from the address bar has never worked since this crap started happening over a month ago, while the youtu.be form may or may not work but can often be made to work using one or other of the methods in the bag-o-tricks discussed in this thread. And it’s the latter behaviour that is crazy inconsistent.
@DPRK, that’s just a Onebox link, not an embedded video.
It’s linking to a web site called “yewtu.be”, for real. 
Which is just an alternative front end to youtube, but @wolfpup is correct that Discourse did not embed the video. (Even with an “embed” URL:
https://yewtu.be/embed/Lni3YbDRmpY
which also lacks a Onebox tag)
However, by invoking the appropriate trick from the handy bag-o-tricks, the original YouTube video can (eventually, by trying different tricks) be embedded:
I have had all the different types work at one point or another (since the breakage). youtube.com vs. youtu.be, trailing slashes vs. not, etc. None are reliable, but all work some of the time.
All this inconsistency tells me that the URL format is a red herring. There’s some other process going on. Timing seemed like a good bet to me. It may not be the preview generation, exactly, but some other process related to that. It works if you post before that completes.
Let’s see if these all work (they all use a different URL format):
Ok, the only one that didn’t work was this:
https://www.youtube.com/watch?v=ZeyUP4g3oAY/
Didn’t like the trailing slash. But no error, either. I pasted the links in and immediately hit the reply button.
I may have spoken too soon and you may have a point about the timing. Trying to post after a short delay …