I tested the BT connection.
So the Flux unit can only connect to one BT device at a time. In order for the laptop PC to pick up the BT signal from Flux, I had to disconnect my iPhone from the Flux trainer, and then my laptop can find the trainer. Zwift works despite a little slow for the numbers on screen to response to effort. Nonetheless, laptop with wifi can be made to work with Flux without ANT+ dongle.
And my Garmin Fenix 3 with ANT+ connection to speed/cadence/power sensor works the whole time with no problem.