RomanoS @Xuhoimogh98
The correct itinerary is actually given by the SBB trip planner:
Luzern - Lugano
Lugano - Milano
Consequently, the single change of trains needed happens at Lugano, from platform 3 to platform 1.
This is a no-brainer as many people will do this transfer. Simply grab your stuff and prepare yourself before arrival at Lugano, go to the exit doors before arrival, so you are ready to leave the train right when it has arrived in the station.
Kind regards,
Roland
