[greggold]

The matek r24 receiver has a voltage input (up to 34V) on the 7th set of pins. It's reported back in telemetry as RxBt.

I use it to report the total pack voltage via the balance plug in my batteries. You could do it for a single cell in the pack as well

I use a Matek ELRS-R24-P6 ExpressLRS PWM Receiver with 7 sets of pins on my 1m Flash 3D plane, but I have never tried to measure total pack voltage. Now I will try it! I think it should work well to indicate when to land, even if its not quite as good as the Frsky system with an external voltage sensor that monitors all lipo cells in the pack and reports on lowest cell.