The source gives several practical congregation rules:
• The follower recites Qunut as part of the Witr prayer.
• If the prayer leader goes into Ruku before the follower finishes — or even begins — Qunut, and the follower fears missing Ruku, the follower follows the prayer leader.
• If Qunut is omitted by the prayer leader, the follower may recite it only when there is enough time to still catch the Ruku; otherwise the follower follows.
• A latecomer who catches the prayer leader in Ruku of the third Witr rak'ah is treated as having caught the Qunut and does not repeat it while completing missed rak'ahs.