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Replying to @bateskecom and @MicrochipMakes
For the SAMD51 and other platforms, CircuitPython has a cross-platform algorithm (https://github.com/adafruit/circuitpython/blob/master/shared-module/touchio/TouchIn.c) that allows the use of any digital pin, but it requires a 1MΩ resistor pulling each touch line to ground. I did a FeatherWing this way to test it, and it worked quite well!
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