There were/are two issues. I believe the dark style should be all set now. Firefox also has an issue with our DRM system and that actually affects all styles. It wasn’t as noticeable on the light styles since they didn’t have the slowdown issue that the dark style did and that exacerbated the Firefox issue.
You can now use dark and Firefox and it’ll mostly be fine like you can use the lights with Firefox and it’ll mostly be fine. Using chrome or safari however will net the fastest speed and less issues until Firefox either updated itself or I find a fix myself.
To clarify again the dark style was causing the slowdowns that Jayne was experiencing, but Firefox was what causing the embedding issues. Combining these issues is what made the embedding take forever to load on the dark mode.