There seems to be a reluctance to even consider the suggestion I made.
It may have been commented on an rejected for some good reason but I
don't recall seeing it.
Transformer and 2 resistors in basic form.
Connect one leg to Vdd, other via divider to ground and tap to ADC in.
Add cap if desired for noise handling.

Track smoothed minimum and maximum to give loaded full voltage excursion.
Sounds super easy, no body diodes at risk, no diode drops, minimum
components, full cycle of waveform, ... .
?

      R
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