I've fixed it.
When you create a post, you can post a URL, but below it you can upload a thumbnail. I though I had to upload a thumbnail but when you do so, it replaces the video url.
The more you know.
Is there somewhere where we can report UI stuff like this? If you find it and make a post, I'll totally upvote you. It's messed with me in the past too.
Can't speak for OP, but there's an annoying thing going on with links in that it doesn't always actually bring in a thumbnail when you do a link. So you think--oh, I'll just add my own thumbnail too! Then I'll have a link to the video with my custom thumbnail! But what that does is remove the video link while preserving the thumbnail.
It's one of those UI things that I guess hasn't been worked out. Or maybe it's something under the UI with Lemmy itself.
I've fixed it.
When you create a post, you can post a URL, but below it you can upload a thumbnail. I thought I had to upload a thumbnail but when you do so, it replaces the video url.
The more you know.