Take the thruster from the ground to find your 2RM thruster (you only need to clean it once and a full clean may count as part of your first thruster). A thruster will count as long as the bar motion is continuously upwards. This means landing like a jerk will not count. If the bar stops above your head and you’re fighting to press it out, it will count as long as the bar does not descend at any point.
For the triplet, substitute 2 pull-ups and 2 dips for each muscle-up as a progression. Remember, this is two rounds for time, not just 21-15-9!
2 rounds for time:
15 thrusters, 115/75#