Safari > Settings > Advanced > Style sheet.

quiet-linkedin-grass.css

/* Quiet LinkedIn — Grass Edition */

#voyager-feed main[aria-label="Main Feed"] > *,
#voyager-feed .share-box-feed-entry__closed-share-box,
#voyager-feed .share-box-feed-entry,
#voyager-feed .feed-shared-update-v2,
#voyager-feed .occludable-update,
#voyager-feed .update-v2-social-activity,
#voyager-feed .feed-new-update-pill,
#voyager-feed .scaffold-finite-scroll {
  display: none !important;
}

#voyager-feed .scaffold-layout__sidebar,
#voyager-feed .scaffold-layout__aside {
  display: none !important;
}

.news-module,
.feed-shared-news-module {
  display: none !important;
}

/* Grass field replacement */
#voyager-feed main[aria-label="Main Feed"] {
  position: relative !important;
  min-height: 72vh !important;
  max-width: 1000px !important;
  margin: 24px auto !important;
  border-radius: 18px !important;
  overflow: hidden !important;
  background-image:
    linear-gradient(
      rgba(255,255,255,0.15),
      rgba(255,255,255,0.15)
    ),
    url("https://images.unsplash.com/photo-1617280137702-32e761be8b26?q=80&w=1887&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D") !important;
  background-size: cover !important;
  background-position: center !important;
  background-repeat: no-repeat !important;
  box-shadow: 0 6px 28px rgba(0,0,0,0.12) !important;
}

#voyager-feed main[aria-label="Main Feed"]::before {
  content: "Go outside." ;
  position: absolute;
  top: 32px;
  left: 50%;
  transform: translateX(-50%);
  padding: 14px 22px;
  border-radius: 999px;
  background: rgba(255,255,255,0.78);
  backdrop-filter: blur(8px);
  color: #111;
  font: 600 18px/1.2 -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  letter-spacing: 0.01em;
}

#voyager-feed .scaffold-layout,
#voyager-feed .scaffold-layout__inner,
#voyager-feed .scaffold-layout__content {
  display: block !important;
}

a[href="/feed/"],
a[href^="https://www.linkedin.com/feed/"] {
  opacity: 0.35 !important;
}