1. Leave: open the crew's … menu and tap Leave crew. Your shared tickets leave its board right away; your tickets stay in your account.
  2. Owners: make someone else the owner first (Members → Make owner), or delete the crew. If you're the only member, leaving deletes the crew.
  3. Remove a member (owner): Members → Remove. Their shared tickets leave the board right away, and they can't rejoin with a link unless you allow them back (Members → Removed → Allow back).
  4. Delete a crew (owner): … → Delete crew, then type the crew's name. The board, leaderboard, members and invite link go right away. Nobody's tickets are deleted.

Settings → Profile lists every crew you're in with Leave, and Stop sharing with all crews removes every ticket you've shared and turns auto-share and the leaderboard off everywhere. Deleting your account removes you from every crew right away.