Try this
Go to Youtube here,
. Below the video there is a Share button. Click it and then click on "embed". Towards the right you can click a copy button that will copy the embed code above it. Next go to the discord lifeboat site and create a post anywhere and just paste it. That will embed the video in the post. That method works on a lot of websites. Again, it's essentially the same amount of work as copying and pasting the url and using the video posting button you have set up here.