Another option besides the NPE Cable is an old Wahoo ANT Key (30pin connector) and a lightning to 30pin adapter. I don’t think any other options exist to do ANT direct on the iPhone (I.e. to make a USB stick work)
I think the CABLE may have a limitation with TR to only bridge 1 ANT device over (?) while the ANT key probably offers more sensors while requiring the cable connection.
I’ve never personally used the Viiiiva to bridge sensors so cannot speak to that at all.