Can players change after a lineup is confirmed? How will I know?

Yes, players can still change after a lineup is confirmed, usually because of a stand-in. The quickest and most reliable signal is the Slack notification we send as soon as the tournament organiser informs us. It lists both the replaced and the replacing player, together with their Steam profiles. These notifications are sent in your dedicated 24/7 Slack Data channel, opened when you launch to production.