Lazypasting what I wrote earlier when someone else asked something similar:

I get an error when I try to embed something, no matter the type or size. I do not know if the issue is because of the client (Voyager), or the instance. Nowadays I usually just upload it somewhere and link to it instead.

I've used catbox.moe for a long time. It does the job well enough for most cases.

I recently decided to roll my own due to various reasons, so if catbox doesn't do what you need and you're interested in testing mine, give me a DM and I can set you up with login details. It's a work in progress, but it works.