The Tacx Flow, and other smart turbo trainers transmit and receive on Bluetooth as well as ANT+. So for a handheld or laptop with Bluetooth you should be OK with a smart turbo (although there does seem to be a Tacx limitation on the number of ANT+ channels available such that if using a Garmin GPS AND a laptop, one must be on Bluetooth if the other is on ANT+ dongle connection, or two dongles are required).
A heart strap would also need to transmit Bluetooth, though, if there is no ANT capability on the training software device, so for example if it’s a Garmin HRM that only sends ANT+ you’d need the dongle. I bought a dual HRM (sends both ANT+ AND Bluetooth) on Amazon called Coolspro, but I’m sure there are others.
I think a watch that measures and sends HR might work as well. Only issues with an ANT+ dongle for a handheld Apple device are a) that mine (the Wahoo dongle) is designed for the older, larger lightning socket, so I also had to buy an adapter to connect into the current small lightning socket in the Apple handheld; b) the size of the older lightning plug means I have to take the cover off my iPhone or iPad to get it fully in; and c) the device’s power socket is also the lightning socket, so if using the dongle you have to make sure the handheld is well charged before the turbo session. All in all, it’s better to use Bluetooth, which I have found has less dropouts, that are REALLY annoying as all ride data gets lost.
I now use a piece of MacBook s/w called iMazing that lets you find files inside an attached iPad or iPhone, and even incomplete Zwift .fit ride files are stored in the Zwift/activities folder that you can find in iMazing, copy over to the MacBook and then upload to Strava as a manual entry. Any screenshots you take during a Zwift ride are there too. I haven’t found a way of doing that for incomplete Tacx rides. Btw Tacx have a cloud site https://cloud.tacx.com where all your completed rides CAN be uploaded by default so you never lose a ride even if you lose your handheld!
A rambling mind 