Pro tip: If you check the conical URL (youtube.com) first, the Lemmy web UI will help catch reposts before they are accidentally submitted.

programming.dev/post/1466264

I switched from using the short (e.g youtube.be) or external URL mirrors for that same reason, and just let the bots comment with privacy mirrors for those who prefer. Using the conical URL, aside from cross post detection, also ensures the thumbnail image and preview text get cached consistently.