Using Safari on iPhone, iPad and MacBook, X embeds are not great. We and I would imagine other football (it's football not soccer) forums would be in a similar position.

Sometimes they don't show at all, you have to scroll up and down several times for them to load.

They can also get cut off and only show 80% of the embed, quick refresh loads it better.

If you give embeds unlimited width, in dark mode you have a large white box that stretches across the full post when using dark mode. I have filed a bug previously where the reverse was happening and this is the fix apparently. We had a large black box when in light mode, which yes it's fixed but now dark mode has the issue.

Limit embeds to 550px, it does remove the issue somewhat, however it would be nice to just remove that background completely. I can see in the CSS you have tried background none, yet it's not working with Apple devices in Safari which are our most used.

Example.

Unlimited embed width.

550px embed width

I haven't posted as a bug as much of this is difficult to replicate, the loading issues are not persistent where I can post a link and say look, there.

There is, I believe, an open bug report for this