Adi Robertson at The Verge:
"Users must now join the YouTube Partner Program in order to add end cards with external links — a common way for YouTubers to point fans toward merchandise or Patreon pages. This limits the cards to channels with 10,000 total public views or more, once YouTube has approved them for the program."
YouTube is shit for creators. It's always been shit and will continue to be shit for the foreseeable future. But now it's especially shitty when you're a new creator starting out.