It will not work for the 2019 Giant Trance, as that has a 2019 RideControl One switch.
If you contact your local Giant retailer they may be able to order you a replacement 2020 switch (there will be a cost) which will be ANT+ compatible and *should* allow it to work with this app.
Jan, just wanted to make you aware that this app works 100% with the MY2020 Giant eBikes.
Any Giant eBike running the MY20 RideControl One switch is now ANT+ compatible. I work for Giant UK and we have been testing your field on a couple of Garmin 1000s and it appears to work well.
Obviously...