[Update September 2023] Unrounded YouTube by lizardgai4

/* ==UserStyle==
@name           Unrounded YouTube
@namespace      youtube
@version        1.3
@description    Undo YouTube's new rounded corners
@author         lightbeam and lizardgai4
@preprocessor   stylus
@var checkbox pfp "Unround pfps" 0
==/UserStyle== */

@-moz-document domain("youtube.com") {
/* Video player */
.ytd-watch-flexy {
  border-radius: 0 !important;
}
/* Most other things */
.style-scope {
  border-radius: 0 !important;
}
#playlist-thumbnail {
  border-radius: 0 !important;
}
/* Channel icons on end cards */
.ytp-ce-element {
  border-radius: 0 !important;
}
.ytp-ce-element-shadow {
  border-radius: 0 !important;
}
.ytp-ce-expanding-overlay {
  border-radius: 0 !important;
}
.ytp-ce-expanding-overlay-background {
  border-radius: 0 !important;
}
.ytp-ce-expanding-image {
  border-radius: 0 !important;
}
.ytp-videowall-still-image {
  border-radius: 0 !important;
}
/* Stats for Nerds panel */
.ytp-sfn {
  border-radius: 0 !important;
}
.html5-video-info-panel {
  border-radius: 0 !important;
}
/* Video preview in progress bar */
.ytp-rounded-tooltip {
  border-radius: 0 !important;
}
.ytp-tooltip-bg {
  border-radius: 0 !important;
}
/* Game and description */
.ytd-rich-metadata-row-renderer {
  border-radius: 0 !important;
}
/* Unround description box */
.ytd-watch-metadata {
  border-radius: 0 !important;
}
/* Not interested */
#dismissed {
  border-radius: 0 !important;
}
/* Chapters */
.ytd-macro-markers-list-item-renderer {
  border-radius: 0 !important;
}
/* End video cards */
.ytp-ce-video, .ytp-ce-playlist {
    border-radius: 0 !important;
}
}