Embeds have 1px solid white line in certain responsive sizes
Proposed fix: Set the background-color: black on the html element in the iframe. Possibly only in a darkmode if such exists.
Why is this the correct fix ? I think the cause is weird sub pixel roundings (in this case Firefox). We have seen it previously on Chrome also and seems to also be hardware dependent. I doubt this will ever be fixed from browser vendors while setting it black will mask the issue for good.