To add the theme to Jellyfin, copy the following line to Dashboard > Branding > Custom CSS:

@import url("https://cdn.jsdelivr.net/gh/az4if/friday_fin/friday_fin.css");

or,

@import url("https://cdn.jsdelivr.net/gh/az4if/friday_fin/FRIDAY.css");

Tested on Jellyfin v10.11.x

To ensure the theme displays correctly, make sure Backdrops are enabled on every device you intend to use. Without it, the appearance may break.